The study showed that adjusting for interest in STEM women were 10% less likely to chose that career than a male in gender equal countries, so personal preferen

The study showed that adjusting for interest in STEM women were 10% less likely to chose that career than a male in gender equal countries, so personal preference (which you’d expect to match with interest) doesn’t entirely explain it. I don’t think the article cites anything that would support your Japan hypothesis.