This suggests to me an inequitable society. A society where at a young age women are already taught that they aren't supposed to be good at math.
The article you linked had a different take—that women are more adversely affected by pressure than are men.
The article had a different take, because I don't think your hypothesis is true: And I went through the American public school system very recently. There wasn't a single year in which it wasn't drilled into our heads by predominantly female teachers how much better girls are than boys at everything. Boys were the victim of daily jabs. There wasn't a single year in which we weren't told that the only reason girls have been traditionally worse at math is because mean boys make girls think they're worse.
This article...
http://ideas.time.com/2013/02/06/do-teachers-really-discrimi...
...mentions something that I witnessed personally. Teachers tend to despise boys who act like traditional boys. Those boys are treated more harshly. Their answers are never given the benefit of the doubt. They're mad to feel like failures.
So I think the meme of "girls are taught they suck; boys are taught they're great" doesn't apply to the United States, and opposite has likely been true since the 70s or 80s.
Sweden is an example of equality, because even though there are plenty inequitable parts of their society they actively work to make those equitable
I think they spend a lot of time and money giving special treatment to girls and women, trying to close innate performance gaps. If they wanted to be truly equitable, they'd do the same for boys (and maybe they're starting to, and we'll soon see results).
But even if Sweden were to do that, what then? They've spent a lot of time pursuing equal results, as though it's a goal in and of itself. Why should it be?
If you have two people, one of whom innately excels at math and the other innately excels at editing prose, why not encourage and foster those skills instead of fighting against them? Specialization isn't a bad thing; it's necessary for real progress to be made.