It does indicate that there is some mechanism that affects different genders differently, but that alone is not enough to assume sexism, you need additional evidence to single out that explanation.

I think the gender differences are driven by a combination of genetics, stereotypes, personal preferences, and yes, sexism, acting in a feedback loop. Genetics cause a slight natural difference; this gets summarized as a stereotype; people comparing themselves with the stereotype develop their preferences based on that; and if they don't conform, they are seen as abnormal (e.g. male kindergarten teachers get suspected of pedophilia) and are correspondingly discriminated against.