Yeah I have no idea what this is all about either. I've beaten Omega over 15 times now on Normal and he hasn't dropped his crystal yet...I'm starting to think Square ripped us off with him being able to join the party.
Gamefaqs - Where you TOO can get an extra dose of textual diarrhea.
I'm playing the JP version, so it might differ here. Is that the chest that's to the left at the very entrance of the area? I remember there was a cube there that handed out 5 of each kind of crystal for monster leveling.