That may be true - i.e., that SS were wrong about Conte about what kind of papal error Conte was talking about - but I thought the SS article was very well-docuмented and credible on the point about a pope teaching "as pope" meaning defining ex cathedra, and that errors in teaching by popes, even by councils, outside of defining or declaring something of the faith as revealed by God is possible.
I thought the SS article was well worth the read. As I recall what happened when I commended Salza for his book The Mystery of Predestination According to Scripture, The Church and St. Thomas Aquinas, I'll now jump into my foxhole. 
I've said many times that I think SS do a good job on many subjects.
That said, I also believe they have a bit of tunnel vision, because they tend to mostly see things from the legal/canonical aspect (which is less relavent amidst a state of grave general spiritual necessity, which compels us to to ascend to
theological principles, which are the source of the canon law in the first place):
If I'm driving an accident victim to the emergency room, and breaking the speed limit in the process, it does little good to scold me for breaking the letter of the law, when presumably the legislator would dispense me from obedience to it, if he knew the circuмstances.
And if nevertheless, the legislator should still unreasonably wish that I should obey the law, I would be completely justified (compelled) in disregarding him (Suarez), because as St. Thomas says, "Necessity carries within itself its own dispensation:" His unreasonably opposed will cannot remove the soul from its necessity, but rather increases it.
And that's what Lefebvre did (and what we do today: We're still on our way to the hospital, and the bleeding has only increased).
Jurisdiction is for souls, and not souls for jurisdiction.