: Yes, so could have I. But it is what it is now so what's the best way to
: justify an explanation? Could be that the same hull planform was seen on
: their other cruisers so it gets the cruiser designation from ONI rather
: than another look. Since it's not human tech, there's no specific need to
: have their functions match UNSC equivalents. It could just be for
: record-keeping.

The theories I like best are:
a. the initial distinctions were made without a lot of data, and possibly by people not that knowledgeable of ship classification, and they became known enough and used enough that it was impractical to change them, so newly-observed ships had to be fit in in an awkward way
b. the ship classes are translations

Where do the letters come from, again (CCS, CRS, etc.)? That would really help in figuring it out.