It doesn’t hold up if you talk about cis women either. I know plenty who cannot have children. Menopause also then would make women not-women, right?

There is a bimodal distribution of biological traits related to reproduction. Traditionally, women are defined as members of one of those clusters, the one whose members are generally able to give birth during some period of their lives. This doesn't mean that all members of the cluster can or have or will give birth, but nonetheless the clusters are fairly well-defined for nearly 100% of the population, with trans people being an exception.

Some of the more extreme trans activists seem to want to pretend that these clusters don't exist, which puts them at odds with reality.

Other seem to demand that the clusters shouldn't matter, which I find rather optimistic since they're relevant for reproduction.

Trans rights are a noble goal, but some of the statements made by trans activists are a bit out there.