I am taking it here that "I" refers not to the real person Maxperson, but to Maxperson's PC in a RPG. Otherwise the example makes no sense, because being hidden backstory is a (relational) property of RPG fiction, not a property of things in the world.
First off, he is obviously talking about his character. It would take a deliberately disingenuous reading to conclude otherwise. Second, your being overly strict with word usage to pin him to an argument and position he was not taking. Concealed backstories are a property of things in the real world. Except we usually call them other things. But you could easily have something like a hidden net trap or glass wall in the real world obstructing the ditch. You are using two-dollar words to make your argument sound more significant than it is.