If I recall, SF are buffed regular types. I remember using melee SF and they were... Melee. I think one or two realms snagged cavalry SF. The whole ranged thing happened because ranged was so much more dominant for years. It's like MI before, it had a use but no one could be bothered to try. Melee SF have a use as well.
I think the special ability was that some SF have defensive buffs? There could be either offensive or defensive.
I could also be remembering totally wrong.