Is that really necessary?
Well, let's say somebody who has trained for three months, and somebody who has trained for five years. Whatever
I agree that if you play by that arts rules, a judo guy will be at a huge disadvantage in a boxing match, etc. But that is where mma type sparing comes in. It allows you to actually see how your skills fair against another person in a very open ruleset that allows all kinds of skills to shine. Then the question becomes, why can a 3 month boxer beat a 5 year tkd guy in this ruleset? (just pulling an example out of thin air)