I think the context is really important.

OpenAI has been behind in the AI race since last November. They have been playing catch-up.

They recently released Astra and declared it is AGI. Now they are desperate for anything they can use as evidence for that claim.

In other words: they had clear motive to do anything they could to steal the glory from prominent mathematicians who worked hard on this problem and solved it. And they also cannot prove that said mathematician's data was not accessed by either the model or the OAI users prompting the model.