Why wartime US destroyer escorts were not called frigates

Why did the US Navy not designate Buckley, Edsall, and John C. Butler destroyer escorts as frigates?

The US Navy did not then use frigate as the Royal Navy did; the term returned later as American anti-submarine escort designs converged with foreign frigates.

Frigate terminology returned as FRAM conversions and new American escort designs came to resemble other navies' frigates. Cold War designation politics and a perceived cruiser gap created further pressure to relabel ships. During the Second World War, the United States used destroyer escort rather than the Royal Navy's revived frigate category. The later convergence of mission and design made the foreign term useful, but American classification remained inconsistent enough that labels cannot be read as simple measures of capability.