This is actually a complete and utter misunderstanding of the non-physical.
Most of what you experience non-physically won't be "responsive to your thoughts".
Very few realities seem to be that malleable... and while you might be able to "modify" things from time to time, what you're changing is your subjective experience of the reality you're experiencing.
That's my two cents at least.

This statement seems a little contradictory since you then actually state what you deny before. It's a little confusing. Please clarify, thank you.
Yes of course this very 'subjective experience' you mention is called F2 and you 'modify' or even 'create' it entirely by your beliefs or 'thoughts', mostly subconsciously if you are not lucid / in dreamstate. That is what we call F2 according to Kepple.
The question of the OP also was with regard to Kepple's descriptions of F2/dreamscapes and while he does not use the word 'thought-responsive' he at least says it is constructed by your beliefs, I think he also means mostly subconscious beliefs and creations since we are in the 'dreamworld' then.
Do you call the 'dreamworld' (F2) now not 'the non-physical' anymore? Because that is what you stated before iirc. It surprises me a little. I thought you meant the nonphysical includes thoughts and dreams (to which I would agree).
Other experiencers and authors (probably Leland and Ziewe) used the word 'thought responsive' indeed for these 'dreamy' areas, if I remember correctly. I find it quite adequate and not wrong.
Yes you are right that many or even most realities (F3) do not show this 'malleable'-trait and you cannot change anything there because the scapes and environments there are based on 'collective thought', this is true. But this was said here already and also by Kepple.
However, in some F3 areas you can create/modify individually and consciously - in some cases. Many projectors report these cases. If you create something "in the astral" (F2 or F3) or are "shapeshifting" this is also 'thought responsiveness' imv (works to some degree also in F3 areas). It does not matter if you consciously or subconsciously create because both kinds of thoughts are meant.
So in dreams (F2) you could also create subconsciously the persons, deceased or living ones. This what was this thread is about. I see 'dead' people and living ones from my current life quite often in dreams. It is also possible that you are 'visited' or have a telepathic connection and this is represented. Oftentimes deceased people appear with meaningful and even verifyable informative messages, so this would be another possibilty I would not rule out per se, although the act of self-creation for some (emotional) purpose seems more likely to me in dreams (F2).
For convenience I copy Kepple's F2 description entirely below.
http://www.astralpulse.com/frankkepple.htmlT4) In depth: Focus 2
The region of your Consciousness Continuum that I call Focus 2 is very interesting. Unlike Focus 1, 3 and 4, this area of your consciousness can only be experienced by you. It is an area of individual consensus reality that nobody else has access to apart from you.
Focus 2 of consciousness is the next area inwards, so to speak from F1. Now, anything that ever has, or ever will come about within Focus 1 originates within Focus 2 of consciousness. This is the area of a person’s imagination; it is where all ideas come about, all impressions, gut feelings, etc. Each and every manifestation that is brought into being within Focus 1 oC, absolutely all of it, every invention, every design, every piece of art of any description, etc. without exception originates within Focus 2 of consciousness.
Focus 2 oC is the place the olden day explorers termed the astral. It is perfectly possible to enter this area and engage in whatever belief construct you like in 3D. It’s the place where most of us do our dreaming. If a person develops a degree of lucidity while they are dreaming, then this is where they will have a lucid dream. If they purposely enact some kind of "projection technique" then they can often enter this region with certain expectations, which will pan out as an "astral projection" experience as opposed to a dream or lucid dream. But these actions are all essentially the same. All that changes is your level of awareness and your expectations.
The key fact about engaging with F2 is that all your belief constructs will be represented in front of you in glorious 3D! As F2 is divided into many, many areas which all hold different beliefs, thoughts, memories and experiences from your life, you can engage with these belief constructs as you wish.
There are tremendous joys to be had here. Myself, I love running through all my childhood memories, for example. Anything you ever felt, saw, experienced, etc., etc., in your life, you can “relive” again within Focus 2 and in stunning detail. Absolutely anything and everything your physical senses have ever experienced, and I mean that LITERALLY, is recorded by your senses and “stored” within Focus 2, plus all your dreams too. F2 is where you do your dreaming every night so you are actually well used to this area.
When engaging with F2 worlds, you will find that the characters there can be quite limited in their range of abilities. This is because they are constructs made by you. Dream characters are a typical example of these constructs. When you are in a dream state in F2, your awareness is usually pretty restricted anyway, usually to the scenario depicted, so you don't really notice. If you enter an F2 area while fully aware, you will soon notice something odd if you try to engage these characters in meaningful debate or try to get them to do something other than what they were doing. They come across as being a bit vague and not quite 'all there'. This is one of the BIGGEST differences between F2 and F3. Some people ask how I can tell the difference between F2 'dream' characters and real people in F3. Don't worry, You WILL be able to tell! People in F3 engage in a whole range of actions, communicate with you directly in meaningful dialogue and act in ways that you could not predict, just as they do in F1/physical. This will become obvious to you once you gain a bit of experience of F2 and F3 environments.
I should point out that although this is your own personal area and cannot be experienced directly by others, it is still possible for someone to communicate with somebody else in an F2 state (such as a dream for example - which is just F2 with restricted awareness). Someone else from outside, say F3, can try to communicate telepathically and this communication will hopefully manifest itself in the F2 experiencer's world, perhaps even as a representation of the communicator. With any luck, the communicator may even succeed in raising the F2 experiencer's awareness to an F3 state, resulting in full face to face contact. This can happen in a seamless manner and is another example of 'overlays' in action, in this case F2/F3. This is how it is possible for those who have 'passed over', to use the old terminology, to communicate via dreams with those still residing in the physical.
This is about as far as those olden-day inner explorers went. Some of them tried to venture “beyond” F2 but by and large they were captured by their superstitions when they came across the 3D Blackness or FZ area. Getting lost or getting mutilated by some monster hidden in the dark recesses of 'The Void' was a big thing in those days. The tales of which would be filed alongside all manner of other scary “facts”, such as, if a person travelled at more than 15mph their physical body would fall apart.
But these days the more forward-thinking practitioners realise this infamous Void of old is just an area of 3D Blackness situated between Focus 2 and Focus 3 of consciousness. To followers of the Monroe School, The Void is simply the 3D-Blackness at Focus 21. Simple as that. No superstitious nonsense getting in the way. Just place your Intent and away you go.
So when you “take off” into the 3D Blackness, you generally emerge within Focus 3 of consciousness, or what is becoming commonly known as the Transition Area, where you will come into contact with other people who are very real indeed, not just F2 'dream characters'. It is to F3 that we will turn our attention to next.