It seems meaningless to give starships arbitrary naval analogues. We don't know the specifics of relative shield strength, relative weapon strength, relative sensor capabilities or relative details at all.
Also we don't really know specifics of Starfleet fleet doctrine. Do you need to have escorts around you larger vessels? Can smaller ships play any meaningful role in combat with ships of the line?
Any decent Starfleet admiral is going to know the capabilities of his ships beyond a mere one word designation.
And just as a sidenote, this blurring of ship types and capabilities is happening in the real world too. The USN's littoral combat ships for example switch equipment packages based on which mission they are about to do.