We know that a lot of social psychology research is weak or wrong, and that a few mainstream researchers hold anti-science viewpoints. http://wjh.harvard.edu/~jmitchel/writing/failed_science.htm

We know that toy manufacturers spend a lot of money on research.

So, it's possible that they have a bunch of gently flawed research, and the flaws are magnified through poor reporting, poor understanding, and then implementation into product.

And now we're here, with toyshops segregrated into pink aisles and blue aisles there's no way back.