This is bullshit.
Agreed, the fact that specific times are used is not applicable when it comes to the human sleep cycle. I think a closer generalization would be along the lines of: Sun sets, activity slows, fall asleep, sun begins to rise, wake up.
Our abstraction of the day into hours/minutes/seconds contributes to sleep problems, we sleep better with the cycle of day/night, because we evolved through time that way. "Hard" wake up times are no good when compared to letting the rising sun wake you.
But to be honest, as much as I'd like to, I'll be the last to go to bed early, consequences be damned.