I do think there's a meaningful distinction to be made between something being attributed to a real person and a fictional character being loosely based on real people, though. Like, I think we can be pretty confident that the events in the Epic of Gilgamesh didn't really happen (at least not literally), but if Gilgamesh was, like is generally accepted, a real person, the Gilgamesh in the Epic is most likely supposed to be that guy. Whereas Robin Hood was probably never meant to be any particular person.

That said, do we actually know whether all the stories in the Bible about Jesus were originally about the same individual? The new testament was written decades and centuries after the death of historical Jesus, by people who didn't even live in the region, right? So all the stories the authors heard would have come from traders and missionaries of Christian cults with vocal traditions. That alone is very long game of telephone, but I imagine every town at the time would have at least one person claiming to be messiah, and if one of them became a big enough deal that rumours around him spread beyond town, there would also be bunch of copycats. So a lot of room for mix-ups.

"I am Jesus, your king!" "I heard Jesus was buried like three days ago!" "I uh- I have come back from the dead!" And then he skipped town ASAP.