The examples would illustrate the issue a little better if there were two pin counts with the same shell, eg DE9 and DE15 and maybe two shells with the same pin count (though I'm not aware of such an example).

Without that it is barely worth the distinction.

Yep, was going to comment on this aspect. If you can't have a DB-9 (which would be the large shell but with a bunch of missing pins) they should have just called the m DA-DE or D-(number of pins)