Are there really multiple styles all fighting over being called 'sim?' Why?
Ron Edwards uses "sim" for a particular analytic and classificatory purpose. He is trying to contrast RPGs in which the participants are expected to make decisions drawing upon concerns that come from outside the play of the game itself - these he labels either narrativist or gamist - from RPGs in which the participants (players moreso than GMs) are meant to confine themselves, in deciding how to make decisions in the course of play, to the contents of the game itself.Blame GNS theory.
Within sim, he distinguishes two main approaches:
*Purist-for-system, in which (i) players confine themselves to applying and discovering the consequences of the game system, and (ii) the game system itself aspires to be, and is at least adequate as, a model of the ingame causal processes. Classic Traveller, RQ, RM, GURPS, C&S and HARP are all examples of this.
*High concept, in which the system is not necessarily meant to model in game processes (though it might) but rather to deliver genre-appropriate outcomes, with the players along for the ride. CoC is a classic of this; so is Ars Magica. A lot of White Wolf and 2nd ed AD&D play aspires to this, but Edwards is very down on it because the mechanics won't actually deliver the genre experience unless the GM manipulates and fudges them along the way (rule zero, or "the golden rule" fromWW). I think a lot of ENworld posters play D&D in more-or-less this style.
*High concept, in which the system is not necessarily meant to model in game processes (though it might) but rather to deliver genre-appropriate outcomes, with the players along for the ride. CoC is a classic of this; so is Ars Magica. A lot of White Wolf and 2nd ed AD&D play aspires to this, but Edwards is very down on it because the mechanics won't actually deliver the genre experience unless the GM manipulates and fudges them along the way (rule zero, or "the golden rule" fromWW). I think a lot of ENworld posters play D&D in more-or-less this style.
Notice that purist-for-system play brings with it a type of constraint on mechanics (rules-as-gameworld-physics) that high-concept sim play does not. For instance, the "obscure death" rule in Dragonlance is designed to help support high-concept play, but it doesn't model any ingame causal process. Similarly for action points in 3E Eberron.
By gamism Edwards doesn't mean what most ENworld-ers mean by that (on ENworld, "gamist" tends to be used to mean "uses metagame mechanics"). He means play where players make decisions based on the desire to win. Again, this is not related to any particular style of mechanics. For instance, Gygaxian AD&D is a mix of rules-as-physics mechanics (eg the way weapons are modelled, Vancian casting, the morale and loyalty rules) and metagame mechanics (eg initiative and action economy, hp, saving throws, XP gain), but the default playstyle for Gygaxian D&D is gamist (what Gygax calls "skilled play", which includes what many ENworlders would regard as improper metagaming, like planning spells among casters for optimisation without wondering about how they communicate with one another in game; as well as gaming the GM).
For Edwards's purposes, the goal of winning via skill play is more salient than the mechanical details or so-called Gygaxian naturalism; but for others, including I think many ENworlders, the "naturalism" is highly salient, and makes them think of Gygaxian D&D as a type of sim (not in Edwards's sense, but in the sense of aspiring to present a "naturalistic" gaming experience).
Finally, by "narrativism" Edwards means play that aspires to yield a satisfactory story as a pretty immediate consequence of play, without anyone actually having to take responsibility as a storyteller - the idea is that the mechaincs will be such that if the players do their bit, and the GM does his/her bit, then story will emerge "automatically" with no need for fudging or deliberate authorship. I think among D&D players, especially ENworlders, this is a rather uncommon motivation for play. Most ENworlders, when they talk about "narrative" play, mean something like a game with a high degree of continuity in the fiction, and rich backstory that makes sense of the conflicts in which the PCs find themselves. (The starkest contrast would be play in which the PCs simply start at the entracne to this week's variation on White Plume Mountain, with no backstory continuity beyond the PCs being the same ones.)
Most ENworld "narrative" play is, in Edwards's terms, high concept sim with a high degree of GM force to maintain the coherence of the backstory and continuity - but many of these ENworld players wouldn't label themsevels as sim players because they are not using the terminology for the same classificatory purpose as Edwards is.