I don't think engine correlation necessarily proves anything, on its own. It's worth remembering, though, that chess.com's report a) presents more than merely raw engine correlation, and b) its correlations do not seem to match against hundreds of engines.

But even with all the evidence presented, "proof" is a tricky thing. To what standard would we be trying to prove a claim?

Does this report prove beyond all reasonable doubt that Niemann cheated? I'd say no, but others may disagree.

How about to a preponderance of evidence? Perhaps. But even that is hard to say when no one has yet presented a rigorous defense or set of counterpoints.

In any case, my post wasn't meant to say that Niemann cheated per se. I have no idea, and chess.com themselves may not be able to actually prove whether he did. But I found the report interesting, even beyond the current issue surrounding Niemann and speaking to potential cheating in high-level chess more broadly, and if you re-read my post, I tried not to state anything definitive about whether Hans actually cheated or not.