These all seem to me to be false dichotomies, which assume that it's impossible either for a single creator to have embroidered their story as they went along, or for multiple creators or editors to have changed the story at different points in time.
You know there's no impossibility -- that's why I said "I assign less than 5% probability", I didn't say "I assign 0% probability". I'm talking about the probabilities of each scenario. Conditional and prior.
If you considered that, and you didn't treat "completely fictional" as the default, needing extraordinary evidence to decide against it, but having hardly any evidence in its favour, I think you'd reach the same conclusion as I
You know there's no impossibility -- that's why I said "I assign less than 5% probability", I didn't say "I assign 0% probability". I'm talking about the probabilities of each scenario. Conditional and prior.
In that case substitute "highly improbable" for "impossible" in the grandparent and exactly the same argument still goes through. Why is it improbable for a cult leader to make up a story, and then later decide that they need to embroider the story further to reconcile it with some existing myths? It seems to ...
To break up the awkward silence at the start of a recent Overcoming Bias meetup, I asked everyone present to tell their rationalist origin story - a key event or fact that played a role in their first beginning to aspire to rationality. This worked surprisingly well (and I would recommend it for future meetups).
I think I've already told enough of my own origin story on Overcoming Bias: how I was digging in my parents' yard as a kid and found a tarnished silver amulet inscribed with Bayes's Theorem, and how I wore it to bed that night and dreamed of a woman in white, holding an ancient leather-bound book called Judgment Under Uncertainty: Heuristics and Biases (eds. D. Kahneman, P. Slovic, and A. Tversky, 1982)... but there's no need to go into that again.
So, seriously... how did you originally go down that road?
Added: For some odd reason, many of the commenters here seem to have had a single experience in common - namely, at some point, encountering Overcoming Bias... But I'm especially interested in what it takes to get the transition started - crossing the first divide. This would be very valuable knowledge if it can be generalized. If that did happen at OB, please try to specify what was the crucial "Aha!" insight (down to the specific post if possible).