The Catholic Thing: Tradition, Continuity, and Vatican II By David G. Bonagura, Jr

Yet an effort to avoid polemics is a mere surface reason for Benedict’s choice of the word. By insisting that Vatican II be interpreted in continuity with the Church of all ages, the pope is saying that the council is part of the Church’s Tradition (with a capital “T”), that is, part of the Church’s authoritative interpretation of divine revelation. Vatican II, therefore, is not a “rupture” in the Church’s Tradition (interpretation of God’s word) or traditions (ecclesial practices descended from the Apostles) resulting in a completely new way of believing, as Professor Hans Küng on the Left and the followers of Archbishop Marcel Lefebvre on the Right maintain. For Benedict, Vatican II is a legitimate development in the Church’s ongoing understanding of Christ and His saving message for the world.

With respect to the sentences in bold -- I don't see how the second necessarily follows from the first.