No, each of the airlines have special benefits that are just for their elites, so QF is not unique in this. There is no extra luggage allowance benefit within Oneworld (unlike Star, which does have this as an alliance benefit). QF happens to offer it, but only for WPs and not for AA EXPs. So you will be paying for that 3rd bag (I forget the cost, since I haven't had to pay it in years, but it is substantial, in the USD 100 range). Sometimes being in the QFF plan does have its advantages.