The main argument isn't about prowess; it's about preference.
"Galpin investigated the percent of women in computer classes all around the world. Her number of 26% for the US is slightly higher than I usually hear, probably because it’s older (the percent women in computing has actually gone down over time!). The least sexist countries I can think of – Sweden, New Zealand, Canada, etc – all have somewhere around the same number (30%, 20%, and 24%, respectively). The most sexist countries do extremely well on this metric! The highest numbers on the chart are all from non-Western, non-First-World countries that do middling-to-poor on the Gender Development Index: Thailand with 55%, Guyana with 54%, Malaysia with 51%, Iran with 41%, Zimbabwe with 41%, and Mexico with 39%. Needless to say, Zimbabwe is not exactly famous for its deep commitment to gender equality."
Source: http://slatestarcodex.com/2017/08/07/contra-grant-on-exagger...
I don't think it's clear why both of these occur however and I haven't been convinced that people who try to derive a position solely off societal level trends tend to do anything other than show off their ideological preference on both ends of the debate.
Places where women also have less choice / self-determination. When women get to choose their career path, they do not choose tech. That is the relevant correlation suggested as a cause.
The "young males prefer trucks, young females prefer dolls" split is also found in chimps FWIW.
Interest drives practice and practice drives skill.
The major concerns being how some perceive their prowess -- and who's preference is really deciding the solutions.
Aside: I've been around enough people in the general field to have heard enough thoughts about women in tech... and they're too often ill-reasoned and ill-positioned (relating to prowess and potential)... but that's more circumstantial, I admit.
