Inhibitory trance puts everything to sleep, including your consciousness.
Expansive trance keeps the conscious awareness 'on', and as your senses turn off, your consciousness has more 'room' to expand. There have been studies done to look at this, I cannot remember the particulars, but Jeffrey Mishlove has had various speakers on his youtube channel that talk about this. Specifically in NDE studies, but it's the same principle.
I think it's a brain phenomenon, but that's my opinion.