I recently read this article (“Managers — Look at Your Engineers’ PRs“) and absolutely agree. In fact, I have done this for a couple of years now and I agree that is a valid and valueable source for feedback – besides the 180 degree feedback from colleagues.
However, I wouldnt just use the PRs for individual performance review but also to track the team performance. PRs reveal a lot of team dynamic (how is the communication between team members) and product/software quality. In a more junior team I would also attend a more active role in PRs to support or fill the role of a senior developer.