As I've posted several times now, things can be solved without being pre-authored, or known to anyone in advance of the solution. Mathematics provides the best-known example.But they are really solving the mystery. The mystery is a real thing to be solved.
The way that RPGing (in a well-designed system) produces decision-making under constraints is (obviously) not identical to mathematics. The inference rules are not rules of logical deduction: they are rules of extrapolation from the fiction in accordance with a variety of principles, both global principles (eg the MC's Agenda in AW; the rule for the GM in Burning Wheel that I quoted to you upthread) and principles much more local to the moment of resolution (eg in BW, that a narration of failure must negate the player's intent for their PC's action).
But it is dogma, and dogma contradicted by actual experience, to assert that there is nothing here but collaborative authorship. If that was true, then there would be no difference between playing a RPG and multiple authors collaborating on a novel.