The truth of this was made clear to me when everyone started doing asynchronous online "code reviews" where the reviewers are just looking at the code (in theory, anyway).
That alone eliminated the majority of the benefit of code reviews, where the author of the code walks through it and explains it in real time. It was amazing how many times I'd seen devs get partway into their explanation then stop when doing that gave them an important insight or revelation that otherwise would never have been surfaced.