@Manbearcat
I can tell you why I have doubts about their simulationist character. I'm working through this real-time, so let's see if I change my mind by the end of the post.
In terms of my categories upthread, they fail at (2) because the GM isn't the one extrapolating the internal cause. The player has too much decision-making power.
So let's turn to (1), which is the trickier case.
I think the fact that
the player gets to impose their will on the fiction, and generate consequences, without that being mediated via a dice roll, is what puts pressure on here. I can see your position (I think I can - I'm just about the opposite of a martial artist, but I can read and hopefully understand your words), and so if "impose their will on the fiction" =
the PC imposes their will on the opponent then I can see the simulationist character you're pointing to. But the number of borderline cases - eg marking a dragon while poking it with a dagger, or marking only two of three foes one attacks because of a choice about how to divvy up the foes among the various PCs - makes me think there is sufficient metagame, or at least "fortune in the middle", in there, that it doesn't quite hit the RM/RQ sweet spot.
The fewer the borderline cases, the more the claim to be simulationist. But even that's not quite right: in RM, if you hit a borderline case then you rework the mechanic (or ad hoc it in some fashion - at my table that was generally consensual with the GM in the chair but not the boss); in 4e D&D, you make up some fiction to explain it. Which reinforces the FitM-ish character of 4e.
What do you think?
I'm going to do the same as you (work my way through what you've written in real time and see where I land at the end), but I'm only going to focus on one facet (as I think it might be illuminating).
So, I agree that a singular piece of game engine (in this case, the suite of converging mechanics that make 4e Defenders "work") that either (a) isn't prioritizing as the apex of design and play a very particular form of Simulation-by-referent/model & extrapolation and/or (b) disallows GMs a Sim-driven-veto (again, by referencing their personal model for the situation & employing their personal means of extrapolation) on a case-by-case basis
is a problem for SImulationism design agenda and play priorities.
Now, if the above is true, if you take a game that doesn't enshrine (a) (at all of the design agenda/systemization/play level) and/or doesn't grant that case-by-case GM veto of (b)? That is the mother load of problems for Simulationism concerns it seems to me. But, as I was attempting to draw out above with my Defender mechanics personal anecdote, GMs might disagree on (a) when employing a game mechanic in a moment of play and therefore disagree on whether the GM veto inherent to (b) is necessary for that a particular moment. Both that (a) and (b) (in that moment) depends upon the particular array of information that they are drawing upon.
So I'm going to move on to the bottom half of your post above; "the fewer the borderline cases..."
Let us take a 3.x attempt at "Sim-ifying" D&D 4e Defender mechanics whereby (a) can be said to have attempted to be in play to one measure (execution notwithstanding) and (b) is certainly in play. Here are my thoughts on what a (dysfunctional...as its the only type of conversation I can see in this scenario) conversation around "borderline case" might come up and resolve:
GM: "The zombies are mindless. Your marking and punishing mechanics requires an opponent with a mind. So your Defender stuff doesn't work. That is how the game was designed (here the GM is leaning on my (a) above)."
Player: "Huh? There is no charm tag or anything like it any of my Defender mechanics? How can my Defender stuff be negated by the mindless tag?"
GM: "It doesn't matter. I'm vetoing this corner-case (the GM is exercising (b) above). Marking and punishing an opponent has to rely upon the creature to have an attention span that can be manipulated; a
mind. It doesn't have one. So I'm extrapolating that the mechanics make no sense in this situation. So your stuff doesn't work."
Player: "Wait. So ok. Even creatures with the most primitive neurology...I mean even creatures that aren't possessed of primitive neurology are goal-directed by metabolic and replication processes/imperatives. You mean to tell me that the necrotic energy that imbues these things with animation doesn't given them any semblance of goal-directedness? The sorcerer or necro or whatever doesn't imbue them with any sense of goal-directedness? That makes absolutely no sense. How can they do...anything? Anything at all?"
GM: "Yeah...they're imbued with a goal by their master or Necrotic energy or whatever...but its just so...I guess...primitive...that it doesn't rise to the level of imbuing it with the processing capacity to register your Defender stuff. Mindless. So your Defender stuff doesn't work."
Player: "Ok, so these zombies have no sense of spatial dynamics at all. No sense of themselves moving in space. No sense of objects external to themselves, relative velocities, angles of intercept, etc? How do they move with any purpose or functionality at all? What governs that? Why doesn't
whatever governs that apply to them processing and orienting to my Defender-ey stuff?"
GM: "...because they're
mindless...and the game engine says
mindless means something...and it makes sense to me that
mindless means something. And that something is
your Defender stuff relies upon the ability to influence a mind...even if the mechanics of your Defender stuff doesn't have the Charm tag....so your Defender stuff doesn't work."
That_is_a_mess of a conversation. You can land on either side of that and with righteous indignation at the end of the affair. And I'll bet you any amount of money that there is an overwhelming deluge of 3.x GMs who would land where my 3.x GM landed above. And then there is a subset of them (and probably not a small one) who feels "player entitlement...rules lawyer...douchey player get out of my game."
So where does Simulationism land on that conversation above? It would seem to me that it would land on the GM's take, despite the reality that both (i) a shortcoming of design is readily apparent and invoked (the interaction of Mindless and Charm tags) and (ii) a case for "no GM veto" can be made without even invoking genre logic or drama logic or game layer integrity logic; by merely referencing how goal-directed things do stuff (goal-directed things moving themselves in a 3d environment and interacting purposefully with objects in that 3d environment).