How does Apple calculate the royalty due on my 64GB iPod Touch if I download thousands of songs, turn off wifi, cancel my Apple Music subscription, listen to music for 20 years, then crush my iPod?
The basic expectation for pay-per-play is that the thing doing the playing has to connect back to Apple once in a while so it can report its play count. With my iPod Nano I'm going to connect it to my MacBook regularly so I can load it with new music. That's the whole point of Apple Music - disposable recyclable tunes!
Alternative, perhaps Apple have realised that pay-per-play is a very inefficient system for paying royalties and they offer different levels of pay-per-download instead, so if someone purchases a song in the old-fashioned iTunes way then they artist gets amount X, and if someone stores it for offline playing then the artist gets amount Y where Y < X, because the assumption is that the customer is going to delete the track in the not-too-far-distant future because it's a throw-away.
I'd be interested to know how long the DRM license for an Apple Music make-available-offline download lasts. It doesn't have to be forever, it only needs to last for a month or two. iTunes on the MacBook/PC could keep an eye on license expiry and request a new one from the Apple Server, and the Apple Server would refuse to grant it if the user's Apple Music subscription had expired.
So please don't tell me this isn't possible, or isn't fair to the artist. It could be, if only Apple would put their mind to it. And that would make them start being fair to the most important person in this relationship - ME - because I'm the poor sod who PAYING for it all.