AI and companies reward sociopathic behavior. When he eventually complains to his boss that his work isn't being merged and it's been done for days/weeks/months that will filter up and look bad on the people holding him up.
I'm sure this person's manager knows that having trouble getting PRs reviewed can (but not always) be a signal of a deeper problem. It could be that no one one the team knows the domain, it could be that no one like the person, but most likely it's that the PRs are frequently bad and no one wants to bother.
Or, I might say, why review the PR. Get Claude to do it? Why do I need to spend my time and attention and this person does not?
At that point then disable merge checks and let them merge without a review. If there is a problem it's on them