Again, category error. You've argued for the authority to tell the player that their character wouldn't ask for that. I'm saying I'd tell the player this is how I will adjudicate that action if you insist, but I'm willing to discuss what action will result in your (the player's) intent instead. There's a gulf between these two. I can use genre expectations to constrain how I will adjudicate actions while not constraining players' control over their PCs. The player is free to insist, in my example, and I'd adjudicate the action. These are different categories of things.
I point this out because you're trying to suggest that any limitation, however introduced, validates all limitations. This is the category error. All games introduce constraints on the players -- it's the fundamental purpose of the rules: to constrain play. So, at the high level, your statement is true -- genre expectations are constraints on play. The problem here is that you're equating such a constraint on play as to be equivalent to authority in play. This is the category error. If you're going to suggest that how I constrain my adjudications of actions to be within agreed genre expectations as being the same as me exercising authority over what the character is allowed to think, then there's a category error -- these are not the same kinds of constraints. The existence of one does not imply or condone the existence of another. It's like saying that since you're only dealt 2 cards in Texas Hold Em', that 2s are wild. There's some rough similarity between the two at the surface, but the existence of the first rule doesn't imply or condone the existence of the second. Both, however, can be rules of play (the latter being clearly a table rule).
Ultimately, this discussion hasn't been about whether or not it's good or bad to have anti-"metagaming" rules. I've presented my case as to why I think they are uncessary and often poorly conceived for their purported goals, but if you like them, awesome. The only right way to play is the way that's fun for your table. The point of this argument was, before it seems to have morphed into a play preference argument (and I own my part in that), is whether or not anti-"metagaming" is expected of the rules set. It is not. It is, however, encouraged as part of the rules on discussing and setting table rules to encourage fun play at your table. So, if you like/want them, great! Set up the table rule.