Feminists would like us to think, all of that is due solely to upbringing, but they offer no evidence â" while denouncing detractors as "sexists" themselves.
Untrue. There is plenty of evidence. There are endless studies where girls are quoted directly complaining about how they are put off STEM because of their gender. They get it from all sides - parents, teachers, other students of both genders. It's a social problem.
On the other hand there is zero evidence that girls are genetically predispositioned to be less interested in STEM. Some people try to cite apes playing with toys associated with one gender or another, failing to notice that apes actually have pretty ridged and highly structured societies too.
Even if there were some genetic factor, it doesn't matter. What matters is that girls want to do STEM, but there are barriers in their way because they are girls. We know this because they tell us, and because people observing them (parents, teachers) tell us.
In chess too, for some reason, there are very few female Grandmasters (GMs). It got so embarrassing, a lesser title of Woman Grandmaster (WGM) was introduced... And there are some â" but very few (all of them from countries with "traditional" views on gender-roles, BTW).
So to become a chess grandmaster you need to spend vast amounts of time around other chess players, who are mostly male, learning and improving. You need to immerse yourself in the world of chess as much as the game of chess. It's rare for grandmasters to appear out of nowhere, they tend to be known in chess circles for years before reaching that level. So, it could easily be a case of chess culture putting girls off from participating, the same as with CS.
Unless you are arguing that girls are just less intelligent than boys, and thus less able to become chess grandmasters... But there is a lot of scientific evidence to support the theory that men and women are of equal intelligence at a genetic level.