I think this might be a red herring. All it takes is someone to get an inkling that someone is working on a new approach and seeing some success for OpenAI to fire the AI cannon at the problem. The community seems fairly small (from this outsider's point of view). The idea that the data made it into the training set and that's how the bot figured it out is definitely possible, but I would want to rule out the simpler more direct explanation first.
The fact that this academic sniping can now be done at scale does change the formula though and shouldn't be ignored. The pressure to move math work into secrecy because at the slightest signal OpenAI and Anthropic will start burning tokens for headlines, is bad for math and its bad for everyone.