Code review is (from my point of view) a way to have a second or third person look at the code from a distance, in his own time, with less context than the author. When I write code I'm far into it and stop seeing the bigger picture. When you pair program, I think the same thing happens. Finally there's the end product, which can be looked at from a distance by a reviewer.

While yes, pair programming is preferred over just pushing to master, I think code reviews (and moreover formal code reviews) are better than pair programming for the final OK.