Content ID is never going to be perfect (so there always needs to be an appeal mechanism). But I'd always expected that false matches would be due to some kind of hash collision, not different recordings of the same piece. Because YouTube doesn't know what the composition is, it only compares to other performances (which are under copyright). And the fact that two different pianists could interpret and perform a work…
Here is one example: https://www.youtube.com/watch?v=RxDCgFFBk20
Two of the movements have correct copyright claims for the performance, but another of the movements has a claim for a recording by a different conductor and orchestra. I see this all the time.
Like another person said here, we don't know how Content ID works or what exactly it's looking for, but it's clearly not an "exact match" of sound waves or something: it has to catch covers of compositions that are still under copyright, for example [1].
[1] https://diymusician.cdbaby.com/youtube/posting-cover-songs-o...