I'm currently on 2022.12.3.2 ('21 M3P) and a recent subscribe to Spotify Premium, went with a Duo account for so the Daughter would have her own (I even asked if she's prefer Spotify or Apple Music, she greatly prefer the former, which was a perk for me with the Tesla not having the latter).
Anyway, my playlists/music, etc., is not updating, or it does sometimes, it seems kind of unpredictable. I've logged the car app out and back in, I've reset the car/head unit, I've disconnected the car from the account and reconnected. It syncs and works exactly as expected between my iPhone and desktop (MacOS) app. Add a playlist, shows up. Add or remove songs, those changes are reflected. Whatever, works like it should.
The M3P however, rarely seems to update - you can force an update with a logout >> login, but that's silly. I tried logging in using both my email account and my assigned user ID, same behavior.
I thought it wasn't working at all until I saw a few new songs (in a playlist) show up.
The car is on WiFi in the garage (all that works fine), and additionally has a decent in-car cell connection (just to cover all bases, I tried with WiFi disconnected as well).
It's like it's polling Spotify for changes, but only every N minutes, where that might be 15 or might be 1500. I noticed when it did sync, it wasn't everything, it was like it pulled the first few messages in a queue and then stopped (so left in a partially sync'ed state).
Bummer, the sound quality is great, Spotify totally satisfies my music and podcast needs, and it works great across multiple devices, and including nice integration with our Sonos stuff.