Does lift not vary with angle of attack. At a certain angle of attack the wing produces no lift. The cranked outer part of the wing has a different AoA to the main part of the wing. Hence at S&L the main wing produces lift, but the outer part does not.
You will not get back to 120 flying S&L as the drag is a problem. By diving you reach the Step, and can maintain S&L at 120.