The US population has almost doubled since he wrote that book.

While I can easily believe most specific individual humans could (with skill and training) get a good meal after a few hours spent foraging if considered separately, that is very different from saying that all of the population can be fed that way at the same time.

The carrying capacity of the planet if we’re “in tune with nature” is the pre-farming population, because even neolithic farms were very unnatural things.