Writing for Macworld, iTunes Guy Kirk McElhearn notes that Apple has fixed some inconsistencies with Apple Music: it now uses the same acoustic fingerprinting method as iTunes Match and won’t download DRMed files anymore:
If you had an iTunes Match subscription, matching was done using acoustic fingerprinting; a way of analyzing the music in your audio files to find the correct track in Apple’s huge library of music. If a track didn’t match, it was uploaded.
If you only had an Apple Music subscription, matching was based only on metadata: the track name, artist, and album. And if nothing could be found with this metadata, the track was uploaded. This way of matching tracks is much less precise than acoustic fingerprinting.
If you subscribed to both iTunes Match and Apple Music, then the iTunes Match matching won out; you got the fingerprinting algorithm to match your music. But if you only subscribed to Apple Music, then you get the simpler, less efficient matching. This led to two issues. The first was matching that wasn’t as accurate, and the second was that when you re-downloaded files to another device, those Apple Music matched files had DRM or copy protection. If you let your Apple Music subscription lapse, then you wouldn’t be able to play those files.
Odd that this wasn’t the same from the start, but the upshot seems to be that if you subscribed to iTunes Match and Apple Music because of this discrepancy, you no longer need to have both.