For example, have a look at SteelHelmetAA, which is the model for Steel Helmet we all know and love

It has 4 variants: the human version, Orcish version, Khajiiti version, and Argonian version

They are all used in ArmorSteelHelmetA, however ArmorSteelHelmetA lists only one entry: SteelHelmetAA

Is it some kind of hard-coded standard of assigning specific versions of armor?

I want to duplicate the Steel Helmet and retain its functionality. Do I even have to mind these "special versions"?

EDIT:
Nevermind, I clicked "show all" and the answer presents itself...