So here's the thing. They will release Apple Music for Android... and there's full stdlib of Swift support for Linux? Could it be that the Android app is partly Swift?
Android ships with Bionic libc, which is different from the glibc that is usually shipped in a Linux distro. There are definitely some differences between the two.
Plus the average Android app is very far from the average Linux app. If they were aiming at supporting Android, I think they would have said that instead of Linux.
The key word here is "partly" Swift. I would not put it past Apple to use an intermediary framework that hosts a Swift runtime and calls into native Android APIs. That keeps the non-UI logic in one codebase.
That's more or less what they do with iTunes, isn't it? I recall there being an incomplete library packaged with iTunes once upon a time (with stuff like a stub implementation of Grand Central Dispatch that was neither grand nor dispatching).
Android ships with Bionic libc, which is different from the glibc that is usually shipped in a Linux distro. There are definitely some differences between the two.
Plus the average Android app is very far from the average Linux app. If they were aiming at supporting Android, I think they would have said that instead of Linux.