[FabHK]

They pass a "visual derivative" to "a human", but only after some matrix multiplications etc. that result in extremely low probability false positives.

It could also happen that you lose your phone and "a human" finds it and randomly puts in the correct passcode on the first try and visually inspects your personal images. In fact, that seems vastly more likely [1].

[1] About 4% of smartphones are lost or stolen every year [https://www.mcafee.com/blogs/consumer/family-safety/almost-5... ], but make it just 1/1000, so 1e-3. Then a 6 digit passcode, 1e-6, so we're at 1e-9 per year, or 1000x as likely as being falsely flagged, assuming Apple's numbers (which can easily be achieved by calibrating the threshold).