>I’m still largely puzzled as to why it might have a naturally selected basis.
Well, you just said it yourself: reading is a form of auto-hypnosis. All communication has a hypnotic component. In many ways, hypnosis is synonymous with “learning.”
It has a naturally-selected basis for the same reason that being able to read has a naturally selected basis: it’s just advantageous to be able to learn quickly.
I would argue that while some forms of hypnosis could be considered a vestige of a less cognitively-complex time (thinking of “highway hypnosis” which has no clear evolutionary advantage), other forms of hypnosis represent the absolute pinnacle of cognitive development: everyone who learns a programming language must first hypnotize themselves into learning that language.