> Yeah, I also don't think that's correct, in most cases. React updates the entire tree internally when anything changes, but actually only changes DOM nodes who's prop or state has changed.

That internal tree update is the root cause of all the problems. During that update, React runs all the javascript in the component, and that of all of it's child components, which then run their child components till the entire tree is done.

Sure, only a small part of the actual DOM will change. But the sheer wastage that happens to update that small part is criminal.