They’re not THAT much heavier than a “proper” I beam design you describe. The gain in strength to weight ratio is worth the switch to the X beam design…I don’t think the slight loss of speed of the rotating assembly due to a heavier beam will be noticed, because of how high of a boost level he is putting the car under.
Plus its proven to work. That in itself should be enough.
And this was my 1001st post…wow.