The difference would be that the same iPhone has access to Taylor Swift through Spotify, Apple Music, Play Music (does that even exist anymore?) and so on.
Put the app store on the same level of competition and level the playing field of Spotify vs Apple Music in regards to the 30% subscription fee.
You must have a wildly different experience with YouTube Music then me. This forced migration was the final tipping point to push me to Spotify. YouTube Music's UX is _horrendous_ compared to Google Play Music, and the pre-canned radio stations are almost completely missing.
There are multiple streaming services, but most people won't pay for multiple services, so there is a lock in effect. And Spotify has a higher market share in music streaming than Apple has in cell phones.
Switching my $10/month payment from Spotify to iTunes is negligible compared to replacing a $700+ smartphone (which is likely on a payment plan). And in the latter case I lose access to every single app I have paid for over a decade.
Oh, it's going to be so much fun when Epic wins and Taylor Swift decides to apply the same legal reasoning to the cut she pays Spotify for her music…