I was under the impression they did do audio fingerprinting. Otherwise, you could gain access to a ton of music.

Sort of ironically, the older iTunes Match system did audio fingerprinting, but Apple Music does not. I have gotten some very weird new metadata occasionally since the switch.

For the record, I've never lost any music, and I'm not entirely sure how that's possible short of a catastrophic iTunes bug[1] -- I'm not disputing anyone's stories, but even "post-Cloud" I've never seen iTunes delete files without me actually clicking on delete somewhere. Despite what the blogger was told by the rep, I'm pretty sure that's not how Apple Music is supposed to work. You enable it on a "primary" Mac, it matches tracks to the iTunes Store library, and then it uploads tracks that aren't in that library to iCloud. The files in your original library will be left alone unless you delete the original files.

[1]: Not that "catastrophic iTunes bug" sounds unlikely. I've heard friend-of-a-friend stories about deletion bugs in the recent past.

Even if they do audio fingerprinting the match is simplistic. I have a large collection of different versions of songs, and Shazam identifies them all as the studio version.

Audio fingerprinting is also pretty hit and miss for classical music where the work is the same and the artist differs.