You missed a whole section - a person creates a Lean formalization of #1 and Lean promptly says the AI proof is wrong because it doesn’t prove that formal problem statement.
The question is in the person (or AI) creating the formal problem statement - how do you know it represents the problem the proof is supposed to be for? And the answer is for people in the field, in this case, formalizing the problem and verifying the formalization is easy. It is like generating an public key versus factoring it.