I believe this is because the angle of attack shifts as well. A plane that is generating lift away from the force of gravity, if turned 180 degrees on it's forward facing axis, will generate lift facing towards the force of gravity. The angle of attack needs to change so that the top side (when the plane is upright) of the wing is again at an appropriate angle of attack to generate lift. So the nose ends up pointing more skyward to get the appropriate angle.