Sexism is not defined as things that disproportionally affect people based on sex. Are tampons sexist? Is the vagina itself, sexist?
Whether or not questions around abortion "disproportionally affect" women is not the question. Abortion also disproportionately affects aborted babies, if you believe they're alive. 1-year olds also disproportionally affect women. Should we be able to kill children until the age of 5? Why not?
I think your take from the perspective of categorization is one that tries to blur things intentionally. It may be the case that an organism does or does not "objectively" belong to a race. But that does not mean that the specific attributes of that organism are themselves not objectively measurable. You're just talking about what definitions are being used.
I think that argument is an attempt to derive ethics from words - rather than discovering the scientific process, deciding ethically what is appropriate or desirable, and identifying the language which should be used to describe it. It's backwards.
At some point a fetus goes from necessarily relying on the mother, to being self-sustaining (if fed) even if removed from the mother. That's a knowable thing. If the baby is removed it will either live or die and that is our answer. Call that life, or independence, or whatever. The lens you choose may change where the line is for you, but not when it is crossed.
I would say that if you believe that children should not be killed post-birth, then you are already cognizant of some kind of threshold that exists which is eventually crossed and cannot be undone, after which adults are obliged to attempt care and continued life of the child.
Because we don't have a way to test exactly when a fetus becomes independent, we use heuristics. For the most part, the first trimester we consider dependent; the last trimester we consider independent; in the ambiguous middle trimester we err on the side of the preference of the already-living, and in some places allow abortions through this time even though there may be a chance that the baby is alive and independent.
But these are just heuristics. "The Texas law is far more restrictive." Yes, it is. But you also said "Go from there" and that is what they did. Texas narrowed to a specific criteria that its people perceive to better approximate the threshold for life. "Life" being in this case a catch-all amalgamation of lots of peoples' concepts that mostly approximates the ability to self-sustain under care. It would seem on the surface at least that an organism without a heartbeat is dead-on-arrival while one with a heartbeat at least has a chance.
The way past this for a place like Texas is to propose a new testable threshold and explain why it is not possible for a self-sustaining baby to be exist before then.