Whatever app/service you use with Sign in with Apple credentials are locked to those credentials.
Your information is obfuscated on the other end. While that enhances privacy, it makes leaving Apple's ecosystem a bit harder as those services are tied to the ID Apple gave to the app/service via Sign in with Apple auth process.
You can always just create another account when you leave, but if it's an app/service that retains history, achievements, etc., those will be lost.
That said, Sign in with Apple works on Android devices IF the developer decides to add it to their Android version of their app. While it may be easy to add to an iOS app, it's a royal pain in the rear to setup for Android devices, but once done, maintaining it is easy enough.
The issue I have is making it mandatory for devs who use other third party auth agents.
Google does not require this for Android devs. If they just want to use Facebook auth, they're good to go. They're not forced to add sign in with Google.