@pemerton - I think the issue at hand is that both the orc and door were already present in the fiction, one alive and the other undiscovered, and the players have changed the
state of those things in the fiction but not narrated their presence or absence. That is actually quite different from, say, being able to narrate the presence of a convenient balcony because you rolled really well to jump out of the Duke's window when he discovered you with his wife (as is the case in a game like Houses of the Blooded). To be specific I mean a balcony that was not in any of the GMs plans, maps, or notes, and that only exists because of successes on a die roll allowing the player narrate it into existence.
At least I'm pretty sure that's the sticking point here.
In the fiction the Orc is there, alive and kicking. The player wants a different fiction, where its dead. The game contains a process for transitioning from one to the other fiction: it involves establishing an in-fiction process (ie
I attack the Orc with my sword) and using a real-world resolution method (rolling dice).
In the fiction the wall is there, blocking the PC's way with no evident ways through. The player wants a different fiction, where the wall contains a way through that is (obviously) not currently evident. A game like Burning Wheel or Cortex+ Heroic contains a process for transitioning from one to the other fiction: it involves establishing an in-fiction process (ie
I search the wall for secret doors) and using a real-world resolution method (rolling dice).
If a table wants to introduce a rule that
no door can become part of the shared fiction unless the GM has already written unilaterally into his/her prior secret version of the fiction that's obviously their prerogative. The same thing could be done with the killing of an Orc, too (see eg the Dragonlance modules which use a method at least a bit like this).
Why would one introduce such a rule? Maybe because one enjoys puzzle-solving? Maybe other reasons, though they're not being clearly articulated in this thread.
My point is simply that
killings of Orcs and
discoveries of doors are not different in this respect. And various posters seem to be confusing
metaphysical differences in the real world (eg obvious differences between how living things move from life to death and how architecture is created and explored) with
differences of how fiction is written (in the case of fiction, the process of narrating
Morgan Ironwolf kills the Orc is identical to the process of narrating
Morgan Ironwolf found a secret door in the wall - as illustrated in my two short stories upthread).