In Apple Music you're supposed to be able to stream songs on your iPhone that you have already downloaded or uploaded to your personal library. But the matching doesn't always work right. Sometimes you ask for a live version and get a studio version, for example.
Well, Apple is fixing the problem with a new way of matching the songs. It'll use the song's aural fingerprint, not just a set of metadata. So the accuracy will be better, and the matched songs you get in Apple Music will be DRM-free, too.
The matching technology in Apple Music is the same as that used in iTunes—iTunes Match—which costs $25 year. Apple is said to be slowly rolling out the improved matching in a (free) update to 1%-2% of Apple Music users per day. MS