Here are some quotes. It seems that the Waldenses themselves, from the twelfth century on, believed in the antiquity of their group
"Well before the time of Waldo, in the early twelfth century, a report was written in the chronicle of the abbey of Corbie, telling about the activities of a "peculiar and ancient kind of people" inhabiting the Alps, who learned the Bible by heart and often wandered about as merchants. They despised the ceremonies and customs of the church and showed no regard for images and relics." Monastier p.102
"About 1230 Reinerus, a Dominican, who states that he had been himself a heretic, wrote a treatise against heretics. …The Waldenses: Reinerus begins by saying that these were the most pernicious of all sects for the reason: (1.) because they were the most ancient, more ancient than the Manichaeans or Arians, dating their origin according to some from the time of Pope Sylvester, 314 to 335 A. D. and according to others from the time of the apostles; (2.) because they are more universally spread; (3.) because they have the character of being pious and virtuous, as they believe in the Apostles' creed and are guilty of no other crime than that of blasphemy against the Roman church and clergy. He also states that they were in all the States of Lombardy and Provence.' “Here I have shown abounded Paulicians called Albigenses, etc., — another proof of their identity with Waldenses. “The heretics have more schools than the theologians and more auditors; they hold public disputations and convoke the people to solemn discussions. …They have translated the Old and New Testaments into other tongues. I myself have seen and heard a clownish layman who could repeat the whole of the book of Job by heart and many who were perfectly acquainted with the whole of the New Testament. They reject whatever is not demonstrated by a text in the New Testament; and then he goes on enumerating places where the heretics have churches and schools; all of which shows that dissent was very widely spread in North Italy and the South of France in the thirteenth century, and it corroborates the traditions of the Waldenses, that their doctrines spread at one time over many districts on both sides of the Alps." Jean Leger, General History of the Evangelical Churches of the Piedmontese Valleys
Neander says: “It was not without some foundation of truth that the Waldenses of this
period asserted the high antiquity of their sect, and maintained that from the time of the secularization of the church — that is, as they believed from the time of Constantines' gift to the Roman bishop Silvester — such an opposition as finally broke forth in them, had been existing all along.” Neander's Hist. Chr. Ch., vol. 4, p. 605.