The "fundamental difference" is that there is a causal process involving the player and the fiction - the resolution of the player's declared action causes everyone to agree that the runes reveal a way out - that does not tightly correlate to any causal process within the fiction - it's
not true that any action of the PC's causes the runes to reveal a way out.
It's worth noting that this is not the same sort of case as unadulterated "director stance", because there is another causal process involving the player and the fiction - the resolution of the player's declared action causes everyone to agree that the PC read the runes and thereby learned (i) that they reveal a way out and (ii) what that way out is - that
does tightly correlate to a causal processes within the fiction - the PC's action of reading the runes causes the PC to learn (iii) that the runes reveal a way out and (iv) what that way out is.
(I made this observation upthread in
post 13249 , before posting the account of the runes in
post 14072.)
The tension that between resolution like that described in my first paragraph above, and "simulationist" play priorities, has been well-known for over 20 years - see, eg,
here (and was also extensively discussed on these boards around 10 to 15 years ago, in the context of 4e D&D):
Consider Character, Setting, and Situation - and now consider what happens to them, over time. In Simulationist play, cause is the key, the imagined cosmos in action. . . . the relationship is supposed to turn out a certain way or set of ways, since what goes on "ought" to go on, based on internal logic instead of intrusive agenda. . . .
Resolution mechanics, in Simulationist design, boil down to asking about the cause of what, which is to say, what performances are important during play. These vary widely, including internal states, interactions and expressions, physical motions (most games), and even decisions. Two games may be equally Simulationist even if one concerns coping with childhood trauma and the other concerns blasting villains with lightning bolts. What makes them Simulationist is the strict adherence to in-game (i.e. pre-established) cause for the outcomes that occur during play.
In the example of the runes, the resolution mechanics do
not strictly adhere to in-game, pre-established cause. Rather, there is an "intrusive agenda" - first, the GM intrudes by announcing a Scene Distinction ("Strange Runes"), and then the player intrudes by establishing a hope for his PC, which feeds into the resolution of his declared action that his PC reads the runes.
Here are two examples I was thinking of this morning, that illustrate how some of the relevant contrasts can be drawn:
Some posters, like me, will remember The Warlock of Firetop Mountain and similar Fighting Fantasy Gamebooks, which were also turned into a simple RPG in the 1980s. In the combat system for this game, a player -
after successfully rolling their attack (Skill vs opponent's Skill) can "test their Luck*. If the Luck roll succeeds, more damage is dealt; if it fails, less damage is dealt.
This resolution system is not ideal from the simulationist perspective, for two reasons. First, there is a type of "rewinding of time" when, having already established that the attack succeeded to a degree, we now go back and find out whether it was especially lucky or unlucky. The luck itself, though, operates in a forward causal direction. This helps those with simulationist priorities tolerate the mechanic despite its rewind-y-ness. Second, there is the fact that
the player has to
choose to find out about their character's luck. So, while we can think of
luck in this game as being an in-fiction phenomenon, the player choosing to activate it sits in tension with simulationist priorities - it is really an introduction of a further element of gambling into the game ("gamisms" is one jargon term for RPG play that emphasises this gambling element). To me, therefore, it's no surprise that really hardcore "simulationist" RPGs don't have this sort of mechanic in them.
The second example: as far as I know, it is (or was) fairly common for a GM in classic D&D play, after rolling a reaction roll, to
make up some bit of backstory to explain the roll. Eg the PC is an Elf, the roll for the NPC is hostile, and the GM makes up a story about the NPC having a grudge against Elves.
This is not ideal from the simulationist perspective either, because the upshot is that there is a bit of the in-game
past, that causally explains the in-game
now (ie the angry reaction of the NPC to the Elf PC), but that was not factored into the roll. Rather, it was authored after the event. Thus, it's no surprise - again - that this isn't a thing in (say) Rolemaster (where the Influence/Interaction resolution table focuses on the character's performance, and not the backstory of the NPCs - the prior attitude of the NPCs is, rather, a factor in the difficulty of the roll, that has to be established
before the dice are rolled). Nevertheless, there are some features of this example which make it
tolerable in some otherwise broadly simulationist play: (i) it doesn't really involve an intrusion of some other priority (the GM is just trying to make sure all the fiction coheres), and (ii) it is done by the GM, not the player, and so doesn't depart from a broader principle that the GM controls the backstory by a combination of literal pre-authorship and in-play heuristics that aspire to emulate pre-authorship.
The runes example can be seen as combining features of both these two examples: player proactivity (like
testing your Luck in Fighting Fantasy), and using a roll that reflects an action occurring in the in-game
now to help establish something about the in-game
past (like the reaction roll example), but centring the player rather than the GM.