Yes, sadly even Archbishop Lefebvre believed that a "good willed" Moslem by being a "good willed" Moslem could be justified, in the state of grace, temple of the Holy Ghost, member of the Church and heir to Heaven. How can the Baptism of desire, a hypothetical case be a known exception to the literal interpretation of EENS? The Archbishop unfortunately did not realize this. For him the Magisterium could not have made a mistake (Letter of 1949). However for him the Magisterium did make a mistake with Vatican II. He was correct the Magisterium was in error but so was he. The Vatican Curia as well as Archbishop Lefebvre were both interpreting Vatican II with the Cushinguite error. Get rid of the error, real restoration will follow. The mistake does not originate in Vatican II. Perhaps if the SSPX realizes this, they can gain canonical status.
Once "traditionalists" think this thing through maybe they will return to the Novus Ordo in time for the next Prayer Meeting at Assisi. For the ones that believe in Invincible Ignorance there is not real reason not to.