The results of the competition suggest otherwise. If you are going to keep repeating the claim that sex and age offer exactly the same physical advantages in all sports, then you're going to have to contend with the actual results that suggest age didn't actually play a big role in this competition, if at all.
But for the sake of argument, let's suppose that you're right. Let's suppose that these 4 kids who finished in the top 6 entered this competition with adults, heroically overcame the injustice of their age-based physical disadvantage, and defeated all the adults. Great. They got the competition they signed up for, and rose to the top. One would expect the competitors in an adult competition to be...adults. Adults who signed up to compete against other adults are not doing anything wrong, just because some kids also chose to sign up. Similarly a man competing in a men's league isn't doing anything wrong, just because some talented woman might occasionally sign up to compete against the men.
In contrast, a man participating in a Women's Skateboarding Contest *is* doing something wrong, because he's entering a contest at which he has a physical advantage, which exists for the sole purpose of excluding him. And if these adults had found a Kids Skateboarding Contest and got in by pretending to be underage, they would also be doing something wrong.
Some absolutely would do it. Some have.
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