That's completely incorrect. They're fat-sparing (to some extent) but it depends on your goals. The fat adaptation drinkwater is doing seems to be of the same type as exercising in a fasted state ("bonk training") that can increase the proportion of fat burned from the ~50/50 mix we normally burn. The studies I've seen have only modest gains (say, 50->55%) so I'm curious how far he can push it.
It is correct, though, that eating fat will spare your carb burning. That might be good for long-distance hiking/running, but is bad for weight loss.