Reading between the lines, one thing that I expect Apple has but may not be discussing -- root-cause replayability post-infection, across all Apple devices.

I.e. infection is eventually discovered, Apple isolates the vulnerability's entry point, then Apple has some ability to re-scan all devices to detect which may have also had the attack targeted against them

Hashing some data that can serve as a fingerprint makes sense from a herd standpoint (hell, even something as simple as call stack after iMessage received)