Apart from that, an airport is a comparatively small area of land that is magnitudes easier to monitor than a border that only exists as a thousands of miles long line on the map, therefore the 100 miles rule should not be applied. And everyone getting off an international flight in the USA has already been searched multiple times.
I mean, that could have been just one person's attempt to justify them operating outside their legal authority. Or it could have been what they were told to say, meaning it was somewhat more official policy (or at least official smokescreen du jour). At any rate, it has been claimed, at least once, not in court but to the press.
I would be delighted for it to not have been an actual administration claim, ever.
As it is the 100 mile zone sweeps in most of the population.