I don't really want to engage with this any further, but I want to point out--again--that I DO NOT require pre-authorship.
I only require that there is SOME answer, and that that answer is not (very specifically) generated in response to the players' choices to investigate. I have (repeatedly!) said that GM pre-authorship is of course the easiest path to having some answer that is not generated in response to the players' actions, but it need not be the only way. You have repeatedly dismissed Clue(do) as an alternative, but there's nothing somehow invalid about using that method in the context of an outright RPG (as opposed to a board game with paper-thin fiction elements).
I know I've badly misunderstood points you've made in this thread, but at this point this is like the fourth time I've explicitly and specifically said I do not require GM pre-authorship. I just expect there to be a solution before the players' investigative choices, not after. I want the solution to be, to use your terminology, "causally upstream" in both the fiction AND the procedure.
Clue(do) is a tangent. We can treat it, and I have mostly been treating it, as a particular variety of GM pre-authorship. For instance, in a RPG with random determination the GM would need to learn what the random determination was, if they were to then use it in all the ways this thread has talked about them using it. And so random determination, say from a chart or draw of cards, would be no different from walking into a game shop and randomly choosing a CoC module to purchase.
Now, if in fact you are saying that a GM can GM a mystery in an "objective" fashion although the answer is unknown
to the GM, because it is hidden inside a sealed envelope, then I have misunderstood your claim, apologise for that, and am interested to learn how you envisage this taking place.
But if that's not what you are saying, then as I said the idea of the GM learning the solution by picking one from a hat rather than writing it up themself is not a relevant detail for the discussion in this thread, for the reasons I just set out.
As for you insistence that there has to be a solution before the players' investigative choices - why? You seem to treat that as being entailed by
is not generated in response to the players' actions, but both phrases have ambiguous plural phrases - choices, actions. And their plural character is not trivial in discussing RPG design: key to "moves snowball" in AW and DW, for instance, is that the outcome of previous player choices/actions affects future framing. Conversely, what is key to the DL modules is that future framing is largely independent of the outcomes of previous player choices/actions.
I posted, not far upthread, an instance of Cthulhu Dark play. At the start of the session, I asked the player of the butler Appleby why Appleby was in London. He told me it was because his master, the Earl, was missing, and hence he (Appleby) had come to London to try and sort out some paperwork.
That establishes a mystery -
what has happened to the Earl. Given that, until play started, no one at the table had ever heard of Appleby or the Earl, let alone had heard that the Earl was missing, it follows that no solution could be generated prior to play. You seem to assert that therefore, of necessity, things cannot be "real"/"objective". But what's your reason? I mean, in play I - as GM - started to form ideas about what had happened to the Earl, which I developed as play unfolded and the players' action declarations demanded more responses from me. I used my developing ideas - of lycanthropes, the links between East African were-hyenas and Central European werewolves, the Earl's lycanthropy - to help shape what I said as I contributed to the shared fiction. One of the players worked out, based on the "clues" that I had provided, that lycanthropes were involved. The players, as their PCs, compared documents that strongly implied - via phrenological resemblances - that the Earl was a were-hyena; and this implication was later confirmed more directly.
Where is the lack of objectivity/reality? Why do you count the inferences drawn on the basis of the hints and foreshadowing I introduced
during play as lacking in "objectivity", when you would count
exactly the same inferences drawn in
exactly the same way on
exactly the same experience of a shared fiction as objective, if I'd done all my decision-making in advance?