Spotify hasn’t allowed in app purchases for years.
Spotify’s complaint was that Apple gave Apple Music special treatment when it came to its platform like how Siri integrates with it and how it was Spotify couldn’t stream directly over the Apple Watch.
Apple opened up both to third parties over a year ago - and Spotify supports neither.
https://community.spotify.com/t5/iOS-iPhone-iPad/Apple-Watch...
I believe that Spotify just don’t want to integrate well with the system so that they can use it as a leverage.
[1]: https://9to5mac.com/2020/04/29/pandora-shows-spotify-how-to-...
I don't think Apple management sat down and thought, right, how do we kneecap competing music streaming providers? Okay lets build Apple Music support for Siri but not Spotify.
It was just that no iOS apps had deep Siri integration and they've been one-offing implementations for common usecases like timers, alarms etc. for the longest time. I assume someone got a project funded by the Music org to go one off the Apple Music usecase as well and here we are.
Apple also has been adding third party intents for years.
With Shortcuts users can add their own Siri actions and third party apps can exposes programming actions.
The thing they (Spotify) are complaining about now with the EU antitrust case is the 30% gate keeping toll Apple charges which is an entirely different thing.
Spotify complained that Apple wouldn’t allow them on the watch. But they still aren’t taking advantage of it even though Pandora has.
There is no way to set that I prefer Spotify, and I've seen a few occasions when CarPlay showed Apple Music when I started a car (might be related to not having Spotify app in the background, but I never digged deeper).