I'm guessing they were just less expensive pack-ins to throw in there... Part of me very vaguely recalls Bane having some Commando Droids, but honestly I don't recall what, when, or where he did. I'm just chalking them up to less expsensive pack-ins in the set, to give it some value and make some stuff people wouldn't mind having extras of.
Kind of like the trooper repacks in the Force Unleashed sets and whatnot.