It doesn't mean anything. Narrativism exists because it was intentionally created. Gamism and Simulationism don't and weren't.
The whole notion of "gamism," "simulationism," and "narrativism" emerged from the brain of Ron Edwards, who was evolving a very particular vision of what kind of RPGs he wanted to play--specifically, Narrativist. This gave rise to a movement of people (first Edwards and then others) consciously and purposefully designing Narrativist games, and so the concept of "narrativism" has developed a coherent meaning.
But "gamism" and "simulationism" are just Edwards trying to explain why other people might play games he didn't like, and... well, to put it bluntly, he didn't have a clue what he was talking about. Nobody designs or plays RPGs with those agendas in mind, there is no "gamist" movement or "simulationist" movement, and so you will never find an RPG that can be cleanly classified as Gamist or Simulationist. D&D certainly can't. About all you can say about D&D is that it isn't a Narrativist game, because it doesn't follow the design approach of that movement.