One thing to consider across Morrison's Batman run was that he did nods to many different eras comics across the run. I don't think he was saying all of the episodes from the 50s were a hallucination, he just used that to nod to some of those comics. There is also a nod to some 50s story with the 'league of Batmen' tales too.

Damian is a nod back to Son of the Demon from the 80s
Man-bat & Talia back to the Adams/O'Neil/Robbins era
Lord Death Man was a single used villain in the New Look 60s & he tied it to some of the odd Japanese Batman takes from 60s/70s.

There are more, but that was just off top of my head.