It is one of the hypotheses. It seems very likely that there were multiple factors at play in the late pleistoscene extinction. A quick search with that topic will provide you with materials. Hunting is a common hypothesis, but it is impossible to prove the causality, and world is usually not that simple. Also, prehistoric human consumption of plant food has most likely been underestimated, as the plant remain fossils have not been able to remain in such climate. Recent dental calculus has shown that humans and their fellow neanderthals ate more plants than it has been originally estimated.

I don't claim to be an expert, but Harari is an excellent story teller. That narrative fits really well with his story.