Transwomen are more likely to be sexually assaulted by men, not women. Your argument is fine except for the point that it ignores the rape that women endure in prisons.
Let's seperate Transphobia from casually dismissing women's claims of concerns for health and safety. The majority of transwomen would not harm women but to pretend that it does not happen is really dismissive and one sided.
https://www.ojp.gov/sites/g/files/xyckuh241/files/media/document/written-martinez.pdf
https://news.wttw.com/2020/02/19/lawsuit-female-prisoner-says-she-was-raped-transgender-inmate
These are the stories of women who suffered rape from Transwomen while in jail. Your argument makes it seem like there are no safety concerns. That's really dissapointing to read. Sexual assault against women is rampant and no men or transwomen should be exepct from critique.