Why postwar records can call a sloop a frigate

Were surviving Royal Navy sloops reclassified as frigates after the war?

They were grouped into a frigate-oriented ASW system, but naval usage continued to identify ships such as Magpie as sloops.

Lists from 1947 grouped sloops, converted destroyers, and other anti-submarine escorts under an emerging frigate framework. Pennant practice and the move toward a common postwar anti-submarine category made frigate labels increasingly visible. That administrative classification did not instantly erase ship type or contemporary naval usage. Philip and his shipmates would still have called Magpie a sloop even when a later list or press account grouped her with frigates. The frigate label may also have been easier to defend in postwar budget rounds because it sounded cheaper.