

No, you’re right, GOOGLE will take the device identifier, but him talking about how he would need to store it, and especially for channels where he talks about user names and passwords really makes me think that he thinks he personally has to do it, with his own backend storing it. (edit: The point is, that he doesn’t HAVE to do it this way. You can, and it gives you more control, but you can let Google do it all. It’s never anonymous with anyone though.)
Apple knows which devices have the app installed. They would be able to link that back to the device if it was demanded, even if it is a bit more obscured.
Just figured I’d add Apples own documentation as well
https://developer.apple.com/documentation/usernotifications/registering-your-app-with-apns