@CluelessBaker
What do you mean by defining characteristic?
Defining of your worth / social status / freedom / security / etc.
Yeah, GC people don't say that.
What they say is that your femaleness defines your sex, that is a real and material thing.
That will materially affect certain things about your life. If you are not a woman, you will not be a mother, have to worry about becoming a mother, or not becoming a mother. You won't have to consider how you might breastfeed your child while continuing to work, or whether it would be better not to work during that time. You won't have to deal with access to sanitary products or bad periods or private places to deal with menstruation. If you live in a place without good access to contraception, or prefer not to use it, you won't have to decide to avoid sex on order to avoid pregnancy. You won't suffer the problems and after-effects of pregnancy. You won't go through menopause with all its effects.
Some of these things are significant enough to actually altar the course of a person's life, even under the best of circumstances.
The point GC people make is that these facts about your sex should not be detrimental to your freedom/worth/social status/security.
But saying that motherhood has nothing to do with differences in career outcomes for women just means you really don't understand why that happens. It's not random, it's in part the nature of being a mother, and in part what society does about that fact.