> If GP is correct, I would think that the point is not to detect departures by people who have overstayed but to more reliably detect all departures, so we can more accurately figure out who has not departed, but should have.
You don't need facial recognition for that, just passport data and passenger manifests. People who didn't break the law aren't going to be evading detection when they buy an airline ticket out of the country.
https://www.cbp.gov/travel/international-visitors/i-94-instr...
> CBP now gathers travelers’ arrival/departure information automatically from their electronic travel records. Because advance information is only transmitted for air and sea travelers, CBP will still issue a paper form I-94 at land border ports of entry.
