That's why in gusts the aircraft always returns to the last roll angle (as long as you don't make control inputs).
Except it doesn't. Because the FSC follows a simple rule number 0.01 = uncommanded movements are not permissible.
Simon, before you engage any further, answer one question for us, please. Without research or thinking about it at all, just as plain as it sounds, based on your current understanding: In high altitude flight with AP = off and sidesticks released - does the airplane maintain level flight?