Apple seems to be somewhat unhappy with nvidia. I think AMD might have ML stuff in their roadmap and Apple is making a bet they will make it before they fix their relationship with nvidia.
From what I hear, Nvidia won't allow Apple to write "bare metal" drivers for their cards. I don't know enough about GPU programming to know exactly what Nvidia is allowing and what they aren't.
I wish we knew the truth behind this. In my opinion Apple is losing more than Nvidia and Nvidia seems to be trying harder to make this work than Apple.
From my understanding, Apple has been writing/maintaining GPU drivers. They've been pretty bad at optimizing them (they also are dropping OpenGL support) so Nvidia wants to maintain drivers themselves. As Apple has been locking down more and more of the OS, it's pushing out Nvidia from creating and distributing drivers. If Apple ceded to Nvidia, I imagine it would be harder for Apple to push things like Metal.
The details of the fight are probably a lot more detailed since they would be negotiating about hardware supply and long term contracts.