I have seen many a PR where it is obvious it is an exploratory work: eg. figuring out how to use an external dependency that is imperfectly or incorrectly documented, etc. (You can claim this should be done ahead of time, but experience tells me you need to code it to learn it)

The emotional toll there is real, but this is exactly the moment when you expose the knowledge of that external dependency to the unbiased party that is the reviewer.

I like combining approvals to satisfy the urge for completion and closure, with a request for fast-follow refactor to better match the newly discovered model of interaction. (The worst code review experience I have seen is when a reviewer accepts it as-is and does a fast follow refactor themselves, depriving the author of the opportunity to learn and remain an expert in that area)