Prior to that, no one knew them to be true of the shared fiction, because the fiction wasn't established.
I believe this goes to your final argument about the nature of gameplay versus fiction. I address that below, but let's say that I find this answer to be special pleading.
This claim is just wrong. The next passage or two will elaborate.
It's not secret backstory used to adjudicate an action - exactly as you say, the players are looking for the GM to narrate some more fiction.
But if the player opens the door to find the secret exit, and the GM (with no reference to action resolution mechanics) drops down a map with no exit, then that is secret backstory used to adjudicate an action.
They're different cases.
A third case, also different, is if the player fails the check - and so opens the door hoping to find (say) a study but instead finds a kitchen. Or a study infested by bookworms (so to check it out involves risking the papers I'm already carrying). Etc.
You keep saying this, but you haven't yet shown me the difference between narrating more fiction and determining action outcomes.
What is the function difference between 'we open the door to the study' and being greeted with an encounter map and 'we look for a map in the study' and being told there is, in fact, no map? Both are requests for the DM to narrate more fiction, yes?
The central conceit here really seems to be revolving around some distinction between an action declaration that you classify as 'asking for more DM fiction' and an action declaration that you classify as 'not asking for more DM fiction.' You haven't clarified the difference. To me, it really seems to differ only in the established conceits of the game. In BW, you don't ask for more fiction, you introduce a desire for specific new fiction and then the DM provides more fiction based on that request, current fiction, established tropes, and mechanics. In more traditional D&D, you interact with the established fiction to and then the DM provides more fiction based on mechanics, established tropes, and prepared notes. The difference between these approaches is really if it's expected for the player to request specific new fiction or is expected to interact with the established fiction.
And that last line really clicked for me jsut now as to what these discussions revolve around. You're approaching this from the mindset that the player should be requesting new fiction, and therefore the DM denying that request based on pre-determined notes is bad play -- it breaks the expectation that players are to introduce new fiction and DMs are to accept or test that fiction using mechanics. Since you're looking at this from only that perspective, you will consistently reject arguments that do not adhere to that concept. Sadly, it seems that you're so wedded to that concept that you cannot even consider not playing that way to be valid, hence the constant creation of threads and posts that keep circling back to this central disagreement.
Personally, I can play either way. I see merits to both styles, and drawbacks to both styles. I prefer to run in the secret backstory mode, as I'm much more comfortable and have much more experience with that playstyle, and my players, on average, prefer it to the other. Heck, I'm having a hell of a time just trying to get them to shift away from requesting rolls to declaring actions, much less introducing new fiction and rolling with the results. But, as a player, I have no real preference either way. My only preference is for a GM that runs an engaging game.
Due to this realization, I'm clipping out the long response to most of the rest of your thread, as it's more of my trying to understand why you don't see the similarity of things. I will address your final argument, as I find it to be reductive and counterproductive.
<snip>
In my view this statement is false, and only gets a semblance of plausibility because the ficitonal is given (metaphorical) reality.
The orc doesn't exist. There are some words about the orc. Then some more words are authored - the orc is dead, say.
The map doesn't exist; nor does the study. There are some words about the study. Then some more words are authored - the study has a map in it. In the real world, we treat the death of a thing as metaphysically different from the presence of an object in a place for reasons to do with differences in causal processes, constitutive independence, etc (the death supervenes on the thing; the object's existence doesn't supervene on the place, so it might have been elsewhere).
But none of these reasons pertain to the authoring of fiction. Adding a sentence to the orc's description: it's dead; and adding a sentence to the study's description; it contains a map; are identical causal processes. And in RPGing terms, that means they are structurally equivalent game moves.
I believe that you do not see a functional difference between killing the orc and creating the map in the library. However, I do believe that you see a difference between killing an orc and finding a ray gun in the library. And, right there, you defeat your own argument.
To delve into this more deeply: You say that the fiction doesn't really exist. Okay, we'll leave aside the game implications of that statement for now and take it for argumentation. Since the fiction doesn't exist, then whatever you author into the fiction doesn't matter: it doesn't exist. Only the act of authoring is a real thing. So, therefore, all acts of authoring are the same. This is absurd, and counterproductive to discussion. If all acts of authoring are the same, then restrictions such as genre appropriateness or fictional positioning don't matter. You've strongly argued that these do matter, so that means that there is a difference in what is authored into the fiction -- some acts of authoring are preferred to others. Since those limitations are subjective -- there's not objective reason that genre appropriateness be a deciding limitation -- then it stands to reason that many things can impact what can be authored depending on the subjective choices of the participants. Following that to it's conclusion, it would seem that, since you yourself argue that there are some limits on authoring and those limits are subjective, that different styles of authoring can exist that serve to limit what can be authored into the fiction. This means that how the fiction is authored in game is actually based on subjective preferences of the players, and that, depending on those preferences, this can very well be a difference between killing an orc and creating a map in the library.
Returning briefly to the game implications of the fiction not existing -- I find this quasi-nihilist as the very concept of the hobby is creating and interacting withing a shared fiction. Stating that it's really a game of make believe and so has no impact in the real world is saying that RPGs can't engage our emotions and thoughts in ways that benefit us outside of telling ourselves a story. There are a number of games out there that are built on the concept of using the fiction as a separation from reality to explore things in reality -- to beat around the bush, so to speak, of emotionally fraught things and find ways to engage them. This definition also completely disregards LARPing, where there's a mix of reality and fiction ongoing. Or even SCA, where there's a fictional construct that's entirely played out in the real world. Your definition of the fiction as not existing is so against so many core tenets of the broader hobby of roleplaying that, as I said, it borders on nihilism.
That wasn't as brief as I expected.