There are athletic sex differences even amongst prepubescent children, mostly caused by the testosterone surge in utero.

See https://womenssportspolicy.org/pre-puberty-male-female-child....

Quite a biased source, no? This doesn't provide evidence that these differences are biological. Boys are much more likely to exercise than girls due to social norms: https://pmc.ncbi.nlm.nih.gov/articles/PMC10478357/.