If Fran had Silver Eyes her illusions wouldn't be illusions anymore, they'd be real things she's literally conjuring form her imagination. Those were fake Leviathans in the water, that's actually the Leviathan. Or she would have summoned Titanica at her full power under Fran's own control. When Illusions stop being fake, then you're just a reality warper.

Also I thought Graf's Golden Eyes merely was a strength booster? He had artificial Golden Eyes if I remember correctly, unless Eos gave him real ones now.