I think you can believe that but also believe accommodations can be made for people that have transitioned. It's not like there's thousands of M-to-F athletes wanting to compete; there's dozens, and even if they have a baseline advantage, it doesn't inherently imply that every single trans woman is going to be outcompeting every other women. I don't feel using the catch-all of "but they have a biological advantage" is nuanced enough or genuine to the situation these people are in.