It's not as simple as "oh hey, different types of brain matter means different abilities". Brain research is in its infancy and in many cases differences observed are extrapolated out. So a research group sees that there's higher blood flow in area X and that area X is activated during answering some basic mathematical problems. Therefore if area X is larger in men, we can presume that men are better at maths right?
Well not really. I'm not going into it in detail, but all you can say is that that might be the case and it's a pretty tenuous link. Investigations of women and their abilities in mathematical problem solving demonstrated involvement of multiple brain regions. It's been proposed that men are better at spatial interpretation of information, which is how a lot of mathematics is taught. Women tend to combine spatial processing with verbal interpretation, which makes it more difficult etc.
Ultimately, the current understanding of how the brain functions is nowhere near advanced enough to make sweeping generalizations like above and the issue is especially confounded here because of massive and longstanding gender biases. Whilst it's plausible that there are gender differences in different academic fields, nobody knows and the one thing I will absolutely guarantee is that it
is not going to be a single factor defining the difference. (I would also caution you on googling something and taking a press release as gospel. At least try to read the underlying research and the field)
Incidentally:
I don't know why you feel that women are so oppressed by the standards of men.
If you seriously think that there's no cultural oppression of women in the mathematical field and otherwise just lol