o1 is several generations old and was released in 2024. Is this some quite old research that took a long time to get published?
Yes, the preprint of the same paper (https://arxiv.org/abs/2412.10849) was first written in December 2024.
Medical research moves. Very. Slowly.
It's also important to note that it beat doctors in diagnosing in a way doctors do not diagnose.