I disagree. I think if the hallucinated part pass the final Lean verification, it would actually be trivial for a mathematician to verify the intent is reflected in the theorem.

And also, in this case, doesn't the mathematician first come up with a theorem and then engage AI to find a proof? I believe that's what Terence did recently by following his Mastodon threads a while ago. Therefore that intent verification can be skipped too. Lean can act as the final arbiter of whether the AI produces something correct or not.