While I don't trust Meta, at all, I can see some reasons for legitimate requests. This could for API access so that the Meta VR headset could work as a substitute for Apples own, in some cases, or Facebook Messenger and iMessage interoperability. I sort of doubt that this is what Meta is trying for, but that would reasonable.
It's probably a bit of both. One part Apple being monopolistic jerks and one part Meta wanting to hoover up even more private data. One issue I can see is that the EU would side with Meta, knowing that the EU privacy laws will protect its citizens, but Apple has to consider the ramification for all users, including those not protect be the GDPR. So Apple is forced to open up and Meta will start using the opening to suck up private information on its American users.
