I think that this is the flawed premise in your basic framework of this. It isn’t as if there was a core group of people, or some privileged collective, who carried the correct canon across the centuries, until the later Church ratified that canon based on nothing except their passed-on secret knowledge. That’s the Roman narrative of how the canon was assembled, and it’s mistaken at its root: there was no secret pristine knowledge, and there was no special group of people. Put it simply, when time came for the Church to openly say that this was the canon and no other, they used records and scholarship of the texts, much like what we’d do today, to determine which works were of an apostolic lineage and which weren’t. Some works, such as the Gospel of Thomas, they excluded not because it was “outside the tradition”; in fact some Church Fathers quotes it as Scripture, and never viewed it as “outside the tradition”. It was rejected simply because scholarship revealed that it was written in the 2nd century, and thus a forgery. And those Fathers, and their “traditions” were simply wrong. Other works, such as the Book of Enoch, they excluded not because it was “outside the tradition” but simply by the study of the OT and NT manuscripts. And yet the Ethiopian Church DOES include the book of Enoch in their bibles, and they believe it IS within the tradition. (And as we know it is even quoted in the New Testament!) And so on. The Third Epistle of Peter. The Gospel of Mary. The churchmen went through each work which claimed to be of inspired authorship, and consulted NOT their traditions, for traditions were disparate and irreconcilable; but rather they consulted scholarship and evidence. The role of the Holy Ghost is evident not in the final assemblage, which can be done by pure scholarship; but rather by the fact that the various lists of the canon in prior centuries, are so similar to it. Even prior to a scientific gathering of the canon, there were people in the prior 2st, 3rd, 4th centuries who had pretty much the final product already in their hand. They couldn’t prove that theirs was the “real” canon, and they certainly never cited some secret Tradition that told them these were the books and no others. They just happened to have these books; others had other books. And in the end it was scientifically determined that theirs was the right canon all along.