Then, how about this. I understand the view of no segregation at all. That's just one big group, no additional work of separation. But how separation by biological sex more meaningful than separation by gender identity?
Men in prison are also massively stronger and build shanks out of everything. If you do have a fight break out, hopefully its segregated by sex, otherwise the woman has no chance in the supermajority case.
Maybe the most important is you don't want prisoners getting pregnant.