The problem I’m actually hearing is that prisons are dehumanizing, unsafe places. The solution to that is abolition — and in the shorter term, a vast improvement in living conditions for incarcerated people, especially those in marginalized groups.
Trans women impostors are a myth. Trans women are dehumanized, threatened, mistreated, and often do not have their identities respect and honored anyway — so there would be no utility in a cis man pretending to be one. And even if that weren’t the case, I’d rather a 100 “fake trans women” receive female treatment than risk a single trans women being treated incorrectly as a man. Those are my values and they are not negotiable.