This report provides a detailed background of Hans' potential cheating, and detailed breakdowns of certain aspects of chess.com's cheat-detection methodology, including previously unknown (or little known) methods such as window focus change event monitoring and post-focus-change move analysis.[1] The report also reveals Niemann's engine move correlations alongside over two dozen chess Grandmasters who have admitted…
Does engine correlation actually prove anything though? Some of the 'statistical analysis' that has been posted on twitter regarding it in the last week has been against hundreds of engines, so 'engine correlation' seems to mean "the move made matched against at least one engine that would have made that move" I think?
This is video explains it pretty well, and seems like a very compelling argument (at least to me): https://www.youtube.com/watch?v=qjtbXxA8Fcc - and just know that the woman talking is a bit hard to understand because of her accent.
... oh, and to address your point about 100's of engines, my first thought was that are only a handful that everyone uses (Stockfish?) (and also, just guessing, but I get the impression that most top engines recommend similar moves, but again, just a guess!).