This may be dumb, but why is Irvine in twice?

Zidane vs Lulu: Lulu, Zidane sucked in almost every way

Rinoa vs Aeris : Aeris, she can become invincible a lot more reliably and doesn't rely on dogs

Wakka vs yuffie : Wakka, easily

Beatrix vs Irvine : Beatrix (though I don't understand this fight)