If that's the case then, I just don't get why Greiver then is such and important icon to Squall. That totally feels random. I mean why would he care so much as to have a necklace of it on him at all times, and other emblems in his room. Why would I the player care about this GF when I know nothing about it or it's history. There'd have to be more to it than that right?

But I have a theory maybe that just occurred to me. If Ultimacia is from the future, then perhaps he's legendary from where he comes in the future? That would thusly be able to tie into the Rinoa=Ult, Squall=Greiver theories.