If you've forgotten what the Required Reason APIs are, here's a refresher from back in June, right after Apple announced them the week of WWDC:
Required Reason APIs. A limited selection of iOS functionality that could potentially be used for fingerprinting, for which an “allowed reason” for usage must be declared in the Privacy Manifest file. (Note that “API” in this context means things like accessing disk space, not service APIs the way we typically think of them in the world of mobile marketing).
Apple has now published the list, and it mostly consists of what you'd expect: APIs that could be used for persistent, app-to-app fingerprinting.
One thing this list probably won't do? Conclusively put an end to 'probabilistic matching' for ad attribution, because that never relied on these APIs in the first place.
But don't let yourself be fooled, because that was never the point of Required Reason APIs. Apple will still get rid of 'probabilistic matching' via a different mechanism: the new, required disclosure of Tracking Domains:
Tracking Domains. Internet domains that an app or SDK connects to that engage in “tracking” (activity related to advertising and data brokers). These must be declared in the Privacy Manifest file, and network requests to these domains will fail until the user gives ATT consent.