I’m willing to concede that Apple’s system is the best designed of the bunch. I’m not willing to call it “private”, however, if it processes unencrypted inputs in the jurisdiction of a nation state with pervasive government surveillance.

I agree from a technical perspective actually. What this system does to counteract that is use a social strategy. The government couldn't break "this specific system" without a lot of people knowing, and that makes it very likely that they would be discovered. And not in a vague way but in a very specific one.

Would this work in some authoritarian countries? No and Apple doesn't care. Would it work in a western one? Maybe.