But I'm still maintaining that an oral tradition can be based on something wholly untrue.
E.g., the female pope myth has not only made the rounds, and was quoted later even in serious historians, but actually had a frikken bust in the vatican made after a while. 'Cause, you know, if she was pope, she got a bust among the pope busts. It took centuries before someone eventually read the records and figured out, "wait a damned minute, that didn't actually happen."
And we're not exactly talking illiterate fishermen there.
We can say that the early Christians had certain traditions. Well, some of them. We don't know where those originated, or when.
More importantly: WHEN are those traditions mentioned?
It would be GRRREAT if we could find a mention of the Last Supper from 40 CE, before Paul wrote about it in 1st Corinthians (estimated 53 to 57 CE), for example. It would nail the issue of a pre-Pauline Christian sect quite nicely, and settle the issue of whether it comes from his vision or an oral tradition.
It would be GRRREAT if we could find a version of the Lord's Prayer from, say, the 60's or even 70's AD, before Matthew wrote it. It would show an oral tradition leading to Matthew indeed.
But we don't actually have those. What we have is at best that a century afterwards someone claims some apostolic origin for such stuff. Earliest we have even claiming such a source is Papias, writing some 50 years after Mark, and claiming that Mark got his stuff directly from Peter and faithfully translating it. Because some Christian priests told Papias so. Whop-de-do, it's like asking some Mormon priests whether Joseph Smith really got his stuff from an angel and golden tables
However that's pretty unbelievable if you think about it, because a fisherman from the Sea Of Galilee, like Peter, would KNOW that it's a small lake in a valley and there's no way for the whole storm incident in Mark to happen. So either that information didn't really come from Peter, or Peter was lying his ass off. It would also lead us to conclude that an uneducated fisherman was a master of foreshadows, layered allegories, etc, if Mark was only writing down what Peter told him, and in fact that Peter was able to do what was all the fashion in Greece among educated elites: compose a story on the structure of their proto-monomyth, namely Homer. It's not impossible, but it seems less likely than that simply we have some priests embellishing the origin of their story to make it more authoritative.
Even more importantly, Papias doesn't really tell us that there was an oral tradition, although it's often taken as such. He went and asked some people, and pretty much filtered it by self-admittedly only listening to those who said what he was wanting to hear. But he doesn't even try, nor even consider trying, to trace the origins of the information he got. Those priests could have made stuff up on the spot, for all we know. We ASSUME, like Papias did, that that information was handed down by oral tradition from the time of Jesus and the apostles, to get... precisely the existence of such an oral tradition. But we don't actually know when or when those stories originated.
Confirming the existence of an oral tradition AFTERWARDS, is really no good, because it doesn't necessarily mean a different origin.
E.g., sure, we can find an "oral tradition" that spammer Keith James Lawrence was found gunned down and with a can of spam shoved down his throat, AFTER Todd F. Bryant wrote the "Death of a Spammer, in a Place Called Hope" story. But that doesn't tell us that Todd F. Bryant was committing to paper an earlier oral tradition. In fact we don't even have to guess. We know he was writing a new fictional story from scratch, and the later oral tradition just repeats his fiction.
Ditto here. Finding something that Paul or Mark or Matthew or Luke or John wrote in an oral tradition in the next century, doesn't mean there was an oral tradition BEFORE them, nor that they were writing based on such an oral tradition. The later oral tradition can jolly well repeat something that originated with Paul or Mark, not the other way around.
