The fallout of this stance is that your definition of railroad is so very different from others definition that using the term simply becomes confusing. Most people would not consider that a railroad. Further, the game that you’ve been describing is so locked into a dungeon only paradigm that I rather doubt it would’ve survived 50 years up to today except in a very small community.
One sort of non-railroad game is classic dungeon-crawling.
Another is scene-framed play of the sort that - in terms of published RPGs - really begins with Prince Valiant in the late 1980s. 4e D&D is the most commercially successful RPG to work with this sort of approach. HeroWars/Quest (Robin Laws), Burning Wheel (Luke Crane) and Marvel Heroic RP/Cortex+-Prime (Cam Banks) are probably the best-known non-D&D RPGs to use this approach.
Another non-railroad approach is "if you do it, you do it" - I think Classic Traveller is the first published RPG with very strong elements of this (although the 1981 revision pushed more towards railroad-y "storytelling"). The phrase itself comes from Apoclaypse World, and AW and some of its successors/descendants are probably the best known RPGs in this style.
There are probably other approaches t0o, for instance exploration-oriented "social crawls".
So I think you are wrong to say that I am "locked into a dungeon only paradigm". What I am locked into are the questions of
who decides what is at stake and
who decides what the goals of play are and
who decides what counts as success/failure. The various approaches that I've described all provide answers to those questions that are not just "the GM decides".
The stakes set by the DM are not secret unless the DM is following a pattern that is not advised for creating a good adventure.
I have seen many adventures where NPCs secretly betray the PCs, although the adventure - and the GM in narrating the fiction to the players - presents the PC as an ally or quest-giver or similar.
I have seen, on these boards, the assertion that it would matter for the GM to decide that an ogre is encountered to the West, if the players decide to go west, or to the East, if the players decide to go east, although the players themselves don't know anything about what is west or what is east.
These are just simple examples of secret stakes. Many more could be given - for instance, the players have their PCs kill a NPC and the GM - relying on their own secret notes about that NPC and the relationships that NPC is part of - then determines consequences that follow from that killing, which then come back to ramify upon the PCs' circumstances. Or the GM deciding that the NPCs do such-and-such a thing, which ramifies upon the PCs' circumstances, because a certain amount of in-game time has passed without the NPCs being stopped.
Secret stakes are
incredibly common, and very widely advocated - often using the language of "consequences" and/or "living, breath world".
That is not how the quantum ogre works. The quantum ogre is still there no matter what.
What is the "what" in
No matter what? And what is the "there" in "the quantum ogre is still there"?
If the direction the players choose is just colour - so if they choose to go west the GM will describe setting suns and ocean shores, while if they choose to go east the GM will describe rising suns and rolling hills - then what does it matter that the GM has decided to frame an ogre either way?
Conversely, suppose the players declare an action to steer clear of ogres (eg suppose that they seek out information about ogre-populated locales; or suppose they use divination magic; etc) and succeed:
then it is ignoring the players' success at action resolution for the GM to frame the PCs into a conflict with an ogre, and the "there" really has nothing to do with it.
Now if we take as a premise that play follows the following procedure:
* The GM draws up and keys a map, and writes up encounter tables etc to supplement the key;
* The players are supposed to make choices about where their PCs go on the map, and those choices are then supposed to interact with the key and the encounter tables to determine what it is the PCs encounter;
The the GM should not be using "quantum ogres". Because that would violate the procedures of play. But (i) I don't think many people who use "quantum ogres" are purporting to use the procedures of play that I've described; and (ii) the procedures of play that I've described will tend to make for pretty low-agency play
unless there is the possibility of the players learning the contents of the key and the tables other than by way of triggering encounters (and D&D tends to lack that possibility outside of the dungeon context). Hence why I find most complaints about "quantum ogres" to be unpersuasive - they are manifestations of an aesthetic preference (ie for play that follows the procedure I've outlined) but don't really connect very much to player agency or railroading.
(EDITed to fix some quote problems.)