I have a similar coworker, but he's not great at prompting, so 10% of the time the AI version of himself makes confident assertions that he did not intend and are clearly not true. Genuinely no idea what I'm supposed to do about it.

Exactly right. He’s good at what he does, except communicating, and people are beginning to associate him with AI slop they don’t have time to read rather than the excellent work he does for them.