Okay, let's go with this, let's say "meaningful choices" is subjective (not conceding the point, just for argument). Can we not then say that, even with the subjectiveness of "meaningful choices" that a game that requires GM approval of player choices must necessarily have fewer "meaningful choices" than a game where players can choose at least some things without GM approval, and therefore less agency, regardless of how you choose to subjectively value "meaningful choices?" Unless you're engaged in bad faith defining that "meaningful choices" has no relation to the words used in the term, this argument falls to the same problem the one that doesn't depend on asserting "meaningful choices" is subjective. I can look at a situation where I must have permission of a GM, even one that is a benevolent dictator and fair, to realize my choice and say that I have less agency here than if I don't have to have the permission of the GM -- if, say, some fair mechanic was employed. That's not the only way this can happen, of course, but as an example it illustrates that the argument that agency is subjective fails because I don't need to rely on the part you deem subjective to arrive at the same conclusion.