B5 was one of my favorite shows, but their willy-nilly approach to ship classification has really been an annoyance over the years. If you look back at the old B5 Wars ships, and B5 Wars was considered canon, they use the same classification for wildly different tonnage ships. Just my pet peeve......
I found it a little annoying too! In all honesty, it seems like the Earth-Membari war era ships followed a roughly sensical pattern, but once the Omega came along, it all went out the window!
However, it is a sci-fi show, so it really can't be objectively "wrong." There is no reason why the EA would have to strictly adhere to a centuries-old classification system, especially when modern navies aren't so good at holding to it! One example is the JMSDF's "
Helicopter Carrying Destroyers" which look an awful lot like an aircraft carrier. Another example is how the USN's guided missile destroyers (DDGs) are the size of WWII-era cruisers, and pack several times the firepower to boot. So, I'm willing to just roll with the punches on this one...