And the most important thing about PCC in my opinion is not the technical aspect (though that's nice) but that Apple views user privacy as something good to be maximized, differing from the view championed by OpenAI and Anthropic (and also adopted by Google and virtually every other major LLM provider by this point) that user interactions must be surveilled for "safety" purposes. The lack of privacy isn't due to a technical limitation--it's intended, and they often brag about it.

If Apple really wanted to maximize privacy, they wouldn't be constantly collecting so much information in the first place (capture the network traffic from an apple device sometime - it's crazy). User interactions on Apple devices definitely seem to be surveilled for "safety" purposes.

From my perspective, Apple's behavior indicates that what they want to maximize is their own control, and their position as the gatekeeper others must pay in order to get access to you.

Something good to be maximized within the constraints of the systems they have to work within. But at some point with enough compromises it becomes maximizing the perception of privacy, not the reality. Promoting these academic techniques may just be perception management on the part of Apple, if the keys are not controlled solely by the user.