It was usual in the Ancient Church to introduce doctrinal statements by phrases like this. The great Decree of Chalcedon begins precisely with these very words. Indeed, the Church always stresses the identity of her faith throughout the ages. This identity and permanence, from Apostolic times, is indeed the most conspicuous token and sign of right faith.
Archaic formulas can be utterly misleading.
Vincent himself was well aware of that. Old customs as such do not guarantee the truth. The true tradition is only the tradition of truth, traditio veritatis. It is not a reference to abstract tradition, to formulas and propositions. It is primarily an appeal to persons, to holy witnesses.