Double Kill, Triple Kill, and Quad Kill are supposed to be awards, not achievements. And why we don't have them, KM only knows. Explosives and Shotguns can kill multiple people simultaneously, and I don't see why kills with successive bullets from any weapon wouldn't count as multi-killing. That would open the award to professional use of things like CMag, Golden Gun, Phantom, RC-P90, and Moonraker.
X kills with AuG in a MWtGG round is just an award for scoring points. Nothing special there.
We have plenty of "experience" awards that have qualifications to them, I don't see why we need a round and match version of License to Kill Achievement.