I think a larger percentage of society would be willing to call this "structural gender-based inequality" rather than sexism, because most people including myself use the word "sexism" to refer to a belief that one sex is less capable or somehow worse than the other.
Similarly, men live fewer years than women, and so receive less retirement benefits. This is a structural gender-correlated inequality (maybe gender-correlated is even better than gender-based) but I don't think many people would call it "sexism against men". They would just say "oh, yeah, that's odd... maybe we should adjust that now that you've brought it to our attention".
Your framing seems to suggest the entities that established the unequal structure are blameless, which I do not think is the case. The leave policies and overall working environments that most of us have came from the belief that men should be dedicated to work and women should stay at home. Whether the people who established these norms had malicious intent or not, they were incorrect and harmed society.
Similarly, men live fewer years than women, and so receive less retirement benefits. This is a structural gender-correlated inequality (maybe gender-correlated is even better than gender-based) but I don't think many people would call it "sexism against men". They would just say "oh, yeah, that's odd... maybe we should adjust that now that you've brought it to our attention".