You've got that backwards. Vatican 2 is the novelty, the sede position of today is the application of tradition and doctrine.
No, this is definitely not true. St. Vincent of Lerins is the author of the
"Vincentian Canon", AD 434, this is "the threefold test of Catholicity laid down by St Vincent of Lérins, namely ‘what has been believed everywhere, always, and by all’. By this triple test of ecuмenicity, antiquity, and consent, the Church is to differentiate between true and false tradition".
Speaking about Liberalism in one of his sermons, Fr. Wathen sums up the Vincentian Canon, which is also applicable to sedeism....
"One of the saints, [St. Vincent of Lerins (died 445)]... made a statement concerning heresy and orthodoxy which I find both wonderfully intriguing as well as important.
He says that the true faith is that which has been believed by all the people all the time. [He is] speaking about all the faithful, all those who are in the Church, which is to say that
any idea that has *not* been held as a part of Catholic doctrine through all the generations of the Church by the vast majority of the people, is not Catholic.Which is to say that at any given time an idea can be widely held even by the vast majority of the people as is liberalism among Catholics today. Also a heretical idea can be shown to have been held by a small group within the Church all through history or during a number of generations of history. But the true doctrine of the Church is that which has been held always by everyone".
According to St. Vincent of Lerins' Canon, sedeism being an "idea that has *not* been held as a part of Catholic doctrine through all the generations of the Church by the vast majority of the people,
is not Catholic."