I can not imagine any country certifying a two seater in which the fin would fail during a rudder reversal in a yaw oscillation. I guess the manufacturers of big A/c said that they did not need such strength because their planes would not be likely to get into such attitudes. Obviously they were wrong and the authorities should not have allowed that standard.
Question is will they do anything about it or will they just say: "Well only happens one in x million flights, uneconomic to fix" and will you or I be on the next flight it happens to?