[tzs]

What part are you skeptical of...the waking up and doing stuff in the pitch black of the night, or the splitting sleep into two segments?

The waking up and doing stuff in the black of night doesn't seem too farfetched, considering that in much of the world a large fraction of people do that nowadays. For a good fraction of the year in much of the world the duration of night is longer than the duration of sleep, so you've really don't have much choice about waking up and doing stuff in the blackness of night unless you just want to lie awake in bed waiting for dawn (or you went to bed late enough to sleep until it is getting light--but then you were awake in the blackness before going to sleep).