Real question is - are we gonna be stuck with just 1 or 2 copies of kahuna for at least a year? Even if we could use him at lv 30 as of now, he'll just be an easy target as our units level up and so do our opponent's, allowing them to earn easy points.
I'm guessing their way of offsetting that is they gave Kahuna above normal stats to make him a bit more future proof.
I remember reading that valiants have 8%(?) higher stats than the normal 5* potential units. Kahuna seems to be in the middle of that 5%(?).