This is a great experience report, some good work done.
However, something that was lost in translation by inexperienced teams is why you use this PR mechanism at all? Unfortunately, the tool vendors have fooled inexperienced devs and their managers that its the best tool for code review. The tool vendors (like gitlab, bitbucket, atlassian or whomever) love that of course, which is why they are silent on this issue.

PRs were designed to code review submissions from a stranger to a core team in the open source world, where they make total sense as an async tool. However, for a team working as core contributors on the same codebase or even same product, there are more efficient and effective ways to do code review without the overhead of PRs. Its the wrong tool for the job for cohesive teams. Use them only very sparingly.