No, it could not. Cryptography can make it as difficult as necessary.
(Not even going to touch how unacceptable it would be for Apple to require that it be able to inspect all internet traffic from a person's phone.)
This is just a failure of imagination. The API could be as restrictive as necessary to ensure privacy.
For example, maybe an app is only authorized to upload specific fields of data and a maximum rate.
How does an app only allowed to upload 10 int32 metrics per day going to secretly upload even a single photo?
> Not even going to touch how unacceptable it would be for Apple to require that it be able to inspect all internet traffic from a person's phone.
There are lots of options for how to implement things so that Apple isn't getting copies of private photos or chat messages. Apple is certainly more trustworthy and accountable than a random app developer from a random foreign country.
Personally, I want a smartphone/app ecosystem that is completely free of any centralization. I'm just talking about how Apple could improve their proprietary/centralized system, which actually does make some of these kinds of things simpler.