Just a thought, and I may expand on this later...
Could this have something to do with the chemical shift of mitragynine or another alkaloid with the standard being brain wave function? And does this resonant frequency cause some kind of rapport to entrain brain waves to a spectra science is not yet familiar with?
In my experience, this particular 'dream-like' state and it's imagery, while lucid and generated by one's own brain is not qualitatively 'dreamed' by the subject's subconscious but rather viewed. In other words, in a lucid dream, though my subconscious is doing the 'dreaming', or spawning the texture, quality, and constituents of the imagery, I am conscious of the fact that I am subconsciously generating what I am consciously experiencing. Hence, a lucid dream.
The lucid state that one may reach in a Kratom experience, however, usually begins while one is still awake and only in a deep, meditative state. The problem is, one cannot be conscious of anything below the threshold of consciousness while still awake or even meditating. However, one can only VIEW intentions, thoughts, memories, etc that are below this threshold if one of the two streams of consciousness is halted so that so that it may be observed (i.e. becoming conscious of subconscious thoughts is like measuring the velocity or direction of a sub-atomic particle - one can either measure the orientation of movement or the rate of movement).
And, again, this is all just a theory but true to my experience, the imagery of such a lucid state induced by Kratom may be inspired by my own thoughts/emotions/etc but these thoughts/emotions/etc are not subconscious and I am also conscious of their origin (whereas the symbolism in a dream must be deciphered after the fact). The contents of this particular lucid-state are not generating the experience and are free of subconscious intent or dialogue - instead, this experience is self-generated (or spawned from the observation of itself). In other words, less a case of storyline or intent/direction and more a matter of feedback and depth of the thought or concept itself.
IN MY EXPERIENCE!!! I'm simply saying a lucid-Kratom experience is generated by the observation of itself (plugging a video-camera into a TV and pointing the lens at the TV screen) and may be infinitely defined and self-contained while a lucid-dream is dreamed/generated by the subconscious while ones awareness/consciousness participates in the dialogue as both creator and creation.
I don't know I spaced out a bit and started rambling.