The fact is, we know from previous experience and from Airbus admission that the fin is very sensitive to excessive sideloads.
WAY back when I was flying the KC-135 (the old water-wagon in the early 70s), the dash 1 cautioned against strong inputs to the rudder noting it could induce significant loads.
It doesn't take but a casual glance to see it IS the largest control surface and thus it can create huge forces. When we were doing hard-over rudder training, it was eye-watering to see how quick a hard-over could roll you through 90deg. BIg surface.. big forces.