The more realistic position of Abp. Lefebvre is that he vacillated back and forth between "hard line" and "soft line" positions, never definitively answering the question of whether Vatican II was Catholic or not.
He, at one time, took a "don't ask, don't tell", position with sevecacantists in his society. He also one time stated: "I would not say that the pope is not the pope. But neither would I say that you cannot say the pope is not the pope."
Of course, he never openly declared for the sedevacantist position, because that would take off the table any possibility of reaching a deal with the modernists in Rome for regularization of his Society.