That's an important thing to note. "Under represented" to them just means "less than whites". There's no rationale, no reasonable understanding. 13% means that they will always be a minority in non-racist sports (cough NBA cough). There will always be outliers (more than the norm) but that will not universally be the case.

It's unreasonable to assume there will be black representation everywhere, and a lot of it at that. And yes, those statistics have other variables like black kids being enthusiastic and working towards those sports.

To further the point, there are more variables than that as hockey (for example) is already a niche sport for much of the U.S., and getting in practice and actually playing as you grow is not very feasible for a lot of communities -- black OR white.