That counts as unauthorized access in the eyes of the law. It’s a private system and they did not have any agreements permitting them to use it as they wanted.

Why would they need to look into Apple’s conduct here? Investigate Beeper for CFAA violations since they cracked into Apple’s internal APIs and ignored large chunks of their ToS in the process.

Of course Apple is going to shut down unauthorized access to their messaging system. They’d lose all customer trust instantly if they didn’t.