The guy is the real thing. His has won the Western States 100, Death Valley 125, etc.
Everything you read about this guy is valid. He is very well known in the ultra-endurance running world. Oddly enough, for all the miles he does, he actually has some solid muscle mass.
I've seen him run on several occasions; perfect bio-mechanics. Flawless body position and gate while running. The strangest thing; when he runs, he doesn't make any noise, none; no foot-strike noise, no breathing, nothing. Just mile after mile of perfect strides. Very strange.
If this guy says he can do it... he can do it.