The new version of this tale is that reality is a simulation. Reality being a dream is so 4th Century China

That’s also what happens at around ~1200 micrograms

A less traveled road to a cool story would be that, while dreaming, you are experiencing unfiltered realities from many nearby timelines simultaneously (hence the fluidity of the reality of dreams, where things change from a moment to the next).

I recently had a very curious experience - my in-dream me recalled a memory from a past dream. It was a really strange feeling that definitely added to the "realism" of the dream.