Idea

After thinking about this, the server response should somehow give you a more detailed information about push notification "status" of a user/device.

The idea is to avoid multiple push registration of a device/pair without relying too much on client cache.

What I'm doing is: caching the PlayFabId of the last logged in user who registered for push notifications on each device. In case the user uninstalls the app or clear the data I lose that information but the device/pair is still registered and will be re registered in the next login.

I don't know how PlayFab handles this internally but in case a same user uses multiple devices we should maybe keep track of registered deviceIDs? push tokens?

I think this can be done, unless the Push Enabled flag shown by the GameManager says that the user is registered for at least one device and it is always the last device where the push registration took place.