I will just side note that in horseback riding, I have been beaten by more than one ten-year-old in equitation ;). Skateboarding has a strong element of style to it as well as skill.

But I don't know enough to know about gender segregation in skateboarding. I did look and it is typical for adults and kids to compete against each other. There are no youth divisions. Hence 12 year old Olympic medalists.

However, some quick research indicates that the gender segregation is to get more women into the sport. Women are skating more and more and without the segregation, inexperienced women would have to skate against experienced men. To work out whether it needs to be gender segregated we would have to pit the top women against the top men and see what happens.