But this can't literally be true, once we get beyond the most austere sort of map-and-key resolution.The difference between this kind of trad and the BitD described is that in trad "what happens" is deduced from how the world was chosen to be. In BitD "what happens" is chosen and how the world was has to be deduced from that.
In the first the initial world state is an input independent of mechanics. In the later the initial world state is an illusion (partly) determined by the output of the mechanics.
For instance, suppose that you're playing a fairly conventional D&D game, and the player declares that their PC wanders through the town at night, singing. The town is a typical fantasy one like Waterdeep or Greyhawk or Hardby or whatever. No GM actually has a map and key and related system for tracking (i) exactly where the PC walks, and (ii) where each guard is at each moment, and (iii) the disposition of each guard towards singers, such that from an initial world state there can be inferred an answer to the question does any guard harass the singing PC?
This is why, upthread, I posted that this is not simply the logic of the setting impressing itself upon the GM. Some decision must be made about what happens, if anything, to the night-strolling singer.
The most traditional way to do this that I know of is a combination of an encounter roll (tells us if a guard, or anyone else, is near the PC) and a reaction roll (tells us how any NPC who is near the PC reacts to them). Those rolls generate how the world is (ie what people with what dispositions it contains at what particular places). The state of the world is the output of these game-mechanical processes.
Does this mean that the initial state of the world is an "illusion"? That's not a description I've ever heard, outside the context of threads like these. The process of encounter rolls and reaction rolls is basically as old as the hobby itself.
I'm not going to comment on BitD, which I don't know well enough; but in Burning Wheel, there are no encounter rolls and reaction rolls. Rather, the Sing roll has been used to perform the same function, namely, on its failure as interpreted by the GM, to determine that the night-strolling singing PC has been harassed by a guard.
This process centres the player (via their decision to make the Sing roll, the stakes that establishes both expressly and implicitly, the general rules for consequence-narration and scene (re)framing etc) in a way that differs from the system of encounter rolls and reaction rolls. That's not an accident: it's a key way in which Burning Wheel is deliberately different from more traditional and classic approaches to FRPGing.
But trying to articulate that difference not by reference to at-the-table processes, but rather in terms of the metaphysics of the fiction ("inorganic", "unconnected", "unfixed", "illusory", etc) is hopeless.