Is there a reason that it’s not available for enterprise developer accounts?

Yeah. I am experiencing this too. Even with just basic content the panning/zooming performance is terrible any time there are > ~10 visible annotations. Using a basic MapPin or MapMarker yields better improvement, but that's not exactly ideal if we want any sort of customization.

I saw the reply from the Frameworks Engineer, however it doesn't appear that all delegate callbacks proper functionally. There's a related question with not much help - https://developer.apple.com/forums/thread/669962

I have experienced the same behavior. No remote notification registration methods are called.