Amazon has also shown that as a company, they're more than willing to engage in anticompetitive behavior when they feel threatened (for example, refusing to sell Chromecasts and Apple TVs, refusing to port Amazon Prime Video to competitors' platforms, etc.) I wouldn't put it past them to drop support for other services when it suits them.
Amazon refuses to even sell Chromecasts or Apple TVs and lies about it if you contact customer support. I've been told that "it's just out of stock", that "we had too many complaints", and even "Apple refuses to let us sell those products".
It's why I canceled Amazon Prime (Funny, after being a customer for over a decade, with Prime since it was offered, cancelling was a single click, with zero follow-up or attempt at retention. Not even a "Oh, hey, why did you decide to cancel after so many years?")
Just canceled too and was surprised how friction free it was. They sent just one follow up email so far trying to tell me about all the "benefits" I'll lose (which were things I never used anyways).
Right but there's no material difference between the two. You just have a choice between which master to serve. Amazon's platform isn't more open, they've just allowed other music services to operate on their platform.
Amazon approval is basically a rubber stamp. Can't say the same for Apple's. I'm also not aware of Amazon denying anything for competitive purposes. Amazon is happy to let Spotify on their platform, despite having a music service of their own, for instance.