No mate. A player has an ability to shape the fictional reality in a significant way that the character doesn't. These are different decision spaces. This is just a fact. You stringing here big words together in attempt to argue that red is blue.
Every RPG player has the ability to "shape the fictional reality" (= contribute to the authoring of a fiction).
As far as "decision space" is concerned, maybe you're using that in some jargonistic sense that I'm not familiar with? The decision I am talking about is the player's decision to have their PC read the runes. They believe, for good reasons, that it is possible that reading the runes will reveal the way out. Likewise the character believes, for good reasons, that it is possible that reading the runes will reveal the way out.
That's what the decision consists in, and it is the same (allowing for the fact that one is an actual decision made by the player of a game, and the other an imagined decision made by a Cunning Expert who is Lost in the Dungeon).
The player has knowledge, that the action declarations can shape the reality far beyond what is possible to the character.
There is no "shape reality". That is some projection of yours.
The player believes, for good reason - because familiar with the rules and mechanics of the game - that reading the runes may reveal a way out. The character believes, for good reason - because a Solitary Traveller and Cunning Expert who knows a thing or two about dungeons and strange runes - that the reading the runes may reveal a way out.
Thus when making decisions based on this knowledge, the player is not operating in the actor stance.
I only know one
meaning of actor stance:
In Actor stance, a person determines a character's decisions and actions using only knowledge and perceptions that the character would have.
The character knows and perceives that the runes might reveal a way out. And this is the basis on which the player makes their decision.
You seem to want to insist that the character does not have any such belief or knowledge. But that is not correct. They do.