What the paper you linked to actually proves:

girls' math scores are just as variable as boys' in some countries and some ethnic groups in the United States such as Asian Americans

I could even grant you that this result transfers to all ethnicities, but still legitimately ask: so what? If yesterday's evidence of differing math scores didn't imply differing ability to you, then equal math scores today shouldn't imply equal ability either. Make up your mind, will ya. Till then I'll consider you to be cherrypicking evidence to support a feel-good conclusion.

I'm guessing you don't have kids yourself. Once you have a girl and a boy the differences are startling and obvious.