. . but my position is that women's sports should be open only to cis women.

Does that disadvantage trans women? Yes, but a vast number of people are unable to participate in competitive sports due to physical limitations. Actually most people are.

And are not cis women being unfairly disadvantaged by trans women in these sports?

Of course trans men are disadvantaged at men's sports, but who is complaining about that?

I have no problem whatever with people being trans (in either direction), but there should be limitations in physical sports.

Of course, trans women could be allowed to compete and their scores disregarded, but of course, they would complain of unfair discrimination, while their intent is to have an unfair advantage.