Example: How does a researcher test whether algorithmically-classified illegal imagery stored on user devices is being scanned and reported home to Apple's servers, and what those bounds of AI-classified criminality are? (presumably with respect to what is illegal in the user's jurisdiction)
Testing by using a test phrase, like in a spam context, is inadequate here as a scanning system can trivially be architected to pass those publicly-known tests, while still overreaching into people's personal files and likely miscategorizing content and intent.
If a user connects via a VPN to Russia for whatever reasons, does their personal content start getting reported to that country's law enforcement by their notion of what is illegal?
Parents often have all sorts of sensitive photos around which are not held with exploitative intent. "Computer says arrest."