Kirk McElhearn, in an update to his recent piece on iCloud Music Library metadata matching:
I’ve been unable to reproduce this issue, and my guess is that there was a glitch with Apple’s servers that has since been corrected. If you only subscribe to Apple Music, or are using it on a free trial, then your songs are matched using metadata only. If you subscribe to both iTunes Match and Apple Music, then iTunes matches your songs using digital fingerprinting.
My guess: Apple’s been rapidly fixing bugs in the backend of Apple Music. I suspect the test that Kirk performed could have been easily reproduced a few days ago, but Apple quickly fixed it once his piece started gaining steam.