Hmmmm, I did forget about the Ultimania entry--though I still think it's most logical that /most/ of the world didn't know about Ultimecia, it is more and more likely that Ultimecia, even if she didn't know exactly what was supposed to happen, was trying to change the way she'd known or read things had to be. Now, whether it was common knowledge or whether she simply found out at some point...

Well, that's all speculation.