I would like to know what exactly sedes disagree with re +ABL's reasoning...
As I indicated above, you falsely appropriate Archbishop Lefebvre as a proponent of your position. While the Archbishop never took the step of publicly declaring the See vacant, deferring to the Church's final decision, he clearly agreed that the papacy is protected by the Holy Spirit from this degree of destruction. He speculated about how this could have happened, given that premise and opts not to make a definitive conclusion, although he repeatedly stated that it's quite possible that the See is vacant. You on the other hand reject the premise entirely and try to co-opt Archbishop Lefebvre as a dogmatic R&R.
It's no different than when the BoDers co-opt the Church Doctors who believed in BoD as if they were defenders of their position that infidels could be saved.