Navies did not all organize ships into classes in the same way. A difference too small to count as a Royal Navy subclass could still produce a separate class elsewhere. Historians moving between navies or periods therefore need to learn the relevant classification practice. They can criticize those distinctions, but should preserve the categories used by the navy they are studying.
Notable Point · 16:28-18:07
Why historians must keep each navy's class distinctions
A design difference that the Royal Navy treated as a variant could define a separate class in another navy.