I've heard accounts of that type of sexism before in Japan. From what I recall hearing many programming shops are all female because the market as a whole is sexist enough that they can get away with paying women lower wages. I have neither cite-able sources nor first hand experience admittedly so feel free to take it with a grain of salt.
My son was in Japan a few years back, and said that there was a 'help wanted' publication for the city he was in. It was released in two volumes, one for men, one for women. I seem to remember he said they were blue and pink, but that might be something my mind added after the fact.
I’ve read the article, but it doesn’t explain why the disparity between sexes.