I was just sent a link to an article in The Psychologist “Sleep on a Problem… It works like a dream” by Josephine Ross
The article gathers loads of anecdotal evidence of creativity in dreams … including, inevitably, those benzine rings!
Personally … while I’m sure that some things happen unconsciously and during sleep, my guess is that 90% of these creativity stories have simpler reasons through selective memory or semi-random inspiration.