Destroyer leaders, frigates, and changing US labels

Why did the US Navy use frigate and destroyer-leader labels for ships much larger than older destroyers?

They covered ships judged too large for ordinary destroyers and too small for cruisers, while repeated postwar reclassifications changed the labels attached to the same hulls.

Destroyer leader became a catch-all label for ships judged too large for ordinary destroyer status and too small for cruiser status. Norfolk moved from the planned anti-submarine cruiser designation CLK-1 to destroyer leader while she was under construction, and the DL symbol became frigate in 1955. Mitscher and John S. McCain likewise moved from gun destroyers through destroyer-leader and frigate labels to guided-missile destroyers. The sequence shows how postwar US nomenclature shifted around the same ships as their missions and weapons changed.