Email info@dataquanta.io and you'll get a reply.
Turn on Airplane Mode and use ExTract — everything works exactly the same, because nothing ever leaves your iPhone. The App Store privacy label reads “Data Not Collected” for the same reason: there is no server, no account, and no analytics.
iOS suspends apps that leave the screen, so a scan can't continue in the background. ExTract keeps your screen awake while a scan runs, so leaving the phone alone on the scan screen works. If you switch apps, reopen ExTract and scan again — finished photos are remembered, so it picks up quickly.
Open Settings and drag the sensitivity slider toward "Fewer, surer matches", then scan again. You always review every photo before anything happens to it.
Drag the slider the other way, toward "More matches". Very small or heavily obscured faces may not be recognised.
Into a folder named after the person, in Files › iCloud Drive › ExTract › Archive (or On My iPhone if iCloud Drive is off). Archiving removes the original from your library once the copy is filed — the standard iOS delete confirmation appears, and it stays recoverable in Recently Deleted for 30 days.
Yes. Deleting uses the standard iOS prompt, and photos stay in Photos › Recently Deleted for 30 days.