Again, there is a massive amount of variability between the experiences of cisgender women. Some cisgender women develop what we would consider male secondary sex characteristics. Some cisgender women are exposed to enough testosterone in puberty to have significant differences in their physiology. What exactly is the difference between that and trans women?

What about trans women who went through puberty with clinically low testosterone levels? What about trans women who don't, and what about cisgender women who go through puberty with clinically high testosterone levels? Are we limiting for testosterone? If so, then you're also banning cisgender women from competing as women. If not, then you don't see trans women as women, given that you are categorically banning them even though many of them are weaker than cisgender women.

Thats it at the end of the day. You can refer to trans women as women without actually thinking that. You see trans women participating in women's sports as men participating in women's sports. You would never want to categorically ban trans women from competition if you didn't. Because trans women are just as varied a group as cisgender women are. We're all women, we all deserve the right to be treated as such. No matter what our testosterone levels are, none of those things make us not real women. So categorically banning us from women's sports is the same as saying "trans women aren't women". Because otherwise we'd be talking about biological advantages and how we can account for them fairly so that all women can compete together.