Kirk McElhearn:

Apple Music, however, works differently. It does not use the more onerous (in time and processing power) acoustic fingerprinting technique, but simply uses the tags your files contains. And it can lead to errors. Here’s an example of how this can be a bit surprising. […]

Since Apple Music matches only using tags, it can’t tell the difference between, say, a studio recording and a live version of a song. Or an explicit version and a clean version. This explains why, for example, Macworld editor Susie Ochs found that a live Phish album was replaced by studio versions of the same tracks.

This explains a lot — like how Apple Music can’t seem to differentiate between acoustic and non-acoustic versions of songs on different albums if the tracks have the same name. But if Apple was able to use acoustic fingerprinting with iTunes Match, why not with Apple Music?

Update: Turns out, this might not be reproducible.