Earlier quoted context omitted.
We tend to start hallucinating when we don't have enough sleep. So generating training data is necessary, but way safer when our muscles are turned off.
in addition: During pre electricity time humen woke up after 4 hours sleep, got awake for some time and then continue to sleep. My guess, this sleep pattern is better for learning.
The confusing thing with this claim is what did people actually do during this time, given bad (and expensive!) lighting only?