Why does Aerith butt in at the 4th Cactuar Crush?

Kid G talks about about cloud being the swordsman the book of kings was describing (I know it’s Gilgamesh) but Aerith awkwardly butts in, cloud seems confused and even Kid G points at cloud but you play as Aerith

Seems weird, why wasn’t it a tag team or have Nanaki do it since his moveset would be perfect for this game and he also was cursed by the cactuar pose thing