Very strangely, they said something directly contradictory. initially that it was impossible to rule out whether bucmkaster’s conversations went into training data. Now they claim the opposite with full confidence.

Is there an alternative link without certificate issues?

It's also possible he shared drafts of the work with someone else, who asked chatgpt to explain it to them with training on. Tao seemed to know lots of details of the work before anything was published, though also worked on the problem in the past with big results so maybe just guessed.