We understand that AI responses are generated through probabilistic means. We also understand that human responses are generated through probabilistic means. Neither is inherently more representative of true understanding than the other.
It's possible has been trained to match a human level of assessment (though imo it's still a ways off) but the AI response is never going to be more representative of true understanding than a human response when it comes to a human question expecting a human answer.
It's quite likely that a given AI will have a more representative response than a given human - but we haven't ever tried to pump so many resources into the training of a single human scholar.
And if we reject determinism then definitionally there's arbitrary probability somewhere in the heart of our decision making (though probably in a very minor role compared to established biases).