"We needed people who would be with us at 2 a.m. committing code so that we could have it in front of AT&T the next day."
That's not about good employees, that's about employees with no lives outside of work. Of course the ones whose job becomes their life will stay longer. It's far more traumatic to leave if you don't know anyone outside of work.
I'll take the four-day workweek start-ups any time over the death march start-ups. And I'll put my own short-week productivity up against anyone's 80-hour week.