This completely misses my point.
Railroading is not something that happens to a character in a fiction. It is a thing that happens to a person in the real world who wants to play a RPG. It's about
who has what sort of ability to contribute to the shared fiction. Talking about physical capacities of both real and imagined people is absolutely irrelevant to it.
This is silly too.
@AbdulAlhazred already gave the example, upthread, of consent to medical procedures, which is generally understood to require
being informed. In the law of sexual assault, the issue of rape by deception is a complicated one, but no one I know who works in that field regards knowledge as obviously irrelevant.
And some of the most paradigm examples of
lacking agency are gambles, like tossing coins or making a lucky dip.
In the context of
the play of a game, the agency of the player is manifested through making choices with the purpose of changing the game in some or other way. Making choices that are, functionally, coin tosses is like choosing whether which of two dice to roll to make my move in snakes and ladders - I mean, someone can make that choice, and even be passionate about it ("I only ever roll my lucky red die!"), but that doesn't mean that they actually have any agency in the game.
The contention you and others really seem to be making is that,
if the PC is ignorant in the fiction, then it is fine for the player to be ignorant at the table. In other words, that it doesn't matter if it is the GM who is deciding all the consequences. Now of course anyone who wants to is free to play that way, but it can hardly be surprising that there might be others who regard that sort of play as a railroad: everything in the fiction is coming from the GM, with the players making essentially random suggestions as to which bit of their stuff the GM should bring into play.