If trans women are women why are you calling them trans?
Women can be sexed at birth as female, male, intersex, neither; women can have genes for XX, XY, XXY, etc; women can have zero or more genitalia; women can have masculine, feminine, androgynous, mixed facial bone structures.
Each of these is a valid subgroup of women which can, if necessary, be described as a subgroup. Normally, just “women” should suffice, but the app linked by this post actively excludes at least one of those subgroups from the label “women”. So it becomes necessary to discuss those subgroups by name, such as “trans women” and “black women”, in order for discourse to occur.
They might be “male at birth” or “intersex at birth” on certain medical paperwork, and those physical sex characteristic will remain unchanged in subgroup “at birth” regardless of any shift in gender or medical alterations to their present-day sex characteristics.
(To avoid any possible confusion, I’m keeping in mind that “male” is sex and “man” is gender, as this is often confused in discussion of these topics. One’s sex is a physical characteristic like one’s eye color or skin tone; most people assume that everyone has just one and that it doesn’t change, neither of which are true. One’s gender is a behavioral characteristic like accent or musical tastes; it can’t be reliably guessed from any physical characteristic, and it can change at any time, either gradually over years or all at once at a coffee shop or anywhere in between.)