I have read that sex offenders in men's prison usually have a pretty rough time. I doubt it would be worse in a women's prison where, on the average, the inmates are less formidable physically. Whether I am right or wrong, the person claiming to be a trans woman might believe that, and be faking gender dysphoria.

 

While I could be wrong, I suspect decisions on where to put transsexuals are more often based on political considerations, rather than the prisoners' physical comfort.