Oh yeah, while I was doing research for the Eirin thing, I happened to find this in the BAiJR article:
The Dream World is another self, says Yagokoro. If the dream is too enjoyable, there's a chance that the real world and the Dream World may switch places, so one must be careful of overdosing.
So the dream selves of AoCF were already a thing in Touhou, including t he idea of switching places with them. The foreshadowing! Too powerful!












