What I'm saying is just let them do what they want to do. Sure, a history/timeline would be a nice thing. But does it really matter? People have their own histories and that should really be enough. An uchiha massacre could have happened to that character. For example, if they're an uchiha and say their parents got killed and they were the only survivor. That's subjectively a massacre.
But like I said, there's also those people who come here thinking the Naruto series is the rule here. Some people still reference Naruto characters. Because those characters have no merit here and technically don't exist at all, does it make them any less important? No, it shouldn't. It's a game and as long as they're happy playing it their way, why not let them play it their way? Telling people 'No' constantly or 'You are playing wrong' will just make them leave this place.
And even if a history is made, do you think the majority of people are going to read it? Probably not. Just probably a few people here on the forums, people who avoid the forums like the plague but still really are into RP, and maybe just some random people browsing the wiki who are bored. I've played with people who reference Oro, Hidan, Zabuza, etc...And I just acknowledge them and keep playing.