Their rules PDF says they won't accept any solution until at least two years after publication in a qualifying outlet. This allows time for the mathematical community to review and accept new results. As the OpenAI proof hasn't been officially published yet, the clock hasn't started ticking.
It’s easy to verify the lean statement, you don’t need to read the proof. That is part of the breakthrough
It is interesting that AI-generated proofs are described as malicious by Lean docs unless reviewed.