Bedrockgames
I post in the voice of Christopher Walken
I think the approach to mystery scenarios you've described is very similar to a simulationist approach to play. There is the information determined ahead of time, and that forms the basis of play, with the GM using all of that to scaffold play and to build upon as needed.
It is probably best to put this aside for now, as it is a detour, but this is a potential area of contention I think in the style itself
Now, I think almost all RPGs have some amount of predetermination going on which is used as a basis to build upon, but with a simulationist approach... and with the mystery approach you're describing... there is much more determined ahead of time, and it is generally treated as inviolate. This last part is key, I think, and it's what @innerdude expressed frustration about in his post.
I think that, similar to what I would say about simulationism, what we're discussing is a process that relies on the illusion of cause and effect. What I would say is that for some, the illusion of cause and effect is likely stronger with a GM determining things ahead of time, since that's similar to how the world works. But it's just their sense of things... their opinion or preference.
Here we have a fundamental disagreement on cause and effect. I wouldn't describe it as illusionary. It is following logic and makes sense, and it isn't like all this stuff is determine by fiat. A lot of players who engage this style want heavy systems for example. So you can have very robust rules systems for simulating things. But I would call it cause and effect without qualifier. I realize you wouldn't agree. But I am just pointing out this disagreement because you state it is illusion as if that is a settled fact and I don't think that description is a settled fact in these discussions (it is a point of view or school of thought)
This is part of the struggle with communication here. There is no "changing" of details in The Between or similar games where the mysteries are not predetermined. It's not a case that something is one way and then it's another. (Or if it is, it's a case of some revelation granting new context to something, which can also happen in the predetermined scenario). The details aren't mutable or amorphous. They're simply not yet known. Once they are established, they are then set. From the player side, there is no real difference. It's only from the GM side that this functions differently.
I get that but I am being broad to cover as much a range of approaches because people take issue with our generalizations. But I would say if the details aren't yet known, then they don't exist until that moment in play. So prior to that moment, there is no objective truth the player could discover. Now perhaps after that moment, it becomes true. But it wasn't true all a long. This is a crucial difference.