Real ship data in Commander is taken from the 'Ship Names.cfg' file, which assigns names and data according to the ship class. Some of the classes added to the game by the MFM (those with class names ending in 'X') aren't represented in the Ship Names file yet.
It's my understanding that Sailor Steve wasn't adding data for them because the 'X' ships are (in theory) supposed to be neutral and wouldn't get sunk anyway, but in practice some of those supposed neutrals actually turn up on the rosters of belligerent nations to make things more interesting for the player.
We were discussing this in the most recent thread for the Ship Names "add on," at least a couple of us are working on personal changes to the Ship Names file to account for all those sinkable neutrals.
http://www.subsim.com/radioroom/showthread.php?t=179806