I’m fascinated that they aren’t requiring an entitlement for all usage of setting & posting notifications through this API. A way to share 64 bits of information (at a time) to any process on the device? That is right in the wheelhouse of tracking a user across apps.

I don’t specifically know the types of things that you’d want to share across apps, but there’s a long history of cross process information channels being removed or restricted.

If the system is storing values for you, and isn’t keeping track of which app they came from, now you’ve got persistent storage across app deletion & re-install, as long as there isn’t a reboot in between.

I think you could easily use it to work around IDFA or IDFV resets, as a simple example.