Rich and Strange Aeons

https://travel.state.gov/content/travel/en/international-travel/before-you-go/covid-19_testing_required_US_Entry.html

"Effective December 6, the  Centers for Disease Control and Prevention (CDC) will require all air passengers two years of age and over entering the United States (including U.S. citizens and Legal Permanent Residents) to present a negative COVID-19 test result a negative taken no more than 1 day before departure"

Bad writing aside ("result a negative"?), what is the point of this requirement? It's not like the US has ever been a low-covid fortress that was usefully keeping out outside cases, like Japan/Taiwan/AU/NZ/Korea. It's not to protect the air passengers, or we would be requiring this of domestic flights. To try to keep out new strains that we don't already have circulating? ...I guess I don't have a simple refutation for that. Except that they allow antigen tests, not just PCR, and you can be early-stage infectious and still negative on antigen. Hell, from a covid-19 challenge trial, you can be infected and still negative on PCR. So it's certainly not bulletproof... whether reduction is worth the hassle is another matter.