I hesitate to speak for Royce White, but that's partly because I'm only familiar with the guy because he's a Republican running for office. I think this is in part intended to benefit his campaign, but he may very well feel strongly about protecting women's sports. I have to admit to needing to deal with some automatic (and potentially unfair) snap judgements about right wingers!

Kanter is a real-deal human rights activist, so this is kinda on-brand for him.

I don't think either have any intention of actually playing. Which would be absurd: either would absolutely destroy any opposition. Basketball is a sport in which the difference in athleticism between males and females is extreme.