This is actually an interesting point. There's a tendency to assume that the core of a story is the same, even if the way it's told is different. I wonder how many generations of retellings it takes for us to notice significant differences.
I think stories about King Arthur would be a good comparison. They fit a similar cultural niche, but we have lots of different versions that were written down over the centuries.
> I wonder how many generations of retellings it takes for us to notice significant differences.
That's not really a sensible question. Compare the 17th-century European story of Cinderella to the 9th-century Chinese story of Ye Xian: https://en.wikipedia.org/wiki/Ye_Xian
The story stayed nearly identical for a period of many centuries. Significant differences could have been introduced at any point, but they weren't.
