Although I wouldn't bet against o3, I think it works to their favor to release it later no matter how well it is doing.

Case 1, does worse than or is on-par with o1: Would be shocking and not a great sign for their test-time compute approach, at least in this domain. Obviously they would not want to release results.

Case 2, slightly better than o1: I think "holding off until they have a chance to tune it further" applies.

Case 3, does much better than o3: They get to release it after another model makes a noticeable improvement on the benchmark, get another good press release to keep hype high, and they get to tune it further before releasing results.