The claim that they 'cannot rule out' using Buckmaster's data isn't true in principle. Trivially, imagine that the model had been trained on data only since Jan

The claim that they 'cannot rule out' using Buckmaster's data isn't true in principle. Trivially, imagine that the model had been trained on data only since Jan 1, but a discovery was published on Jan 2. Whether it's true in practice that's a matter of how their systems' functioning & its current state. If they really care about proving this, it's worth an audit. In fact, if anything, they may be able to prove that it hadn't used Buckmaster's inputs, but wouldn't be able to prove that it had.