Most realistically, no one is going to go on the books as the person who voted to repeal the crime of rape.

More pragmatically, repealing a law that someone is in prison for always creates an argument that they shouldn’t be there any more. Often seen with drug legalization, but I’m sure someone would try to argue that because the exact type of sexual assault they were guilty of isn’t a crime anymore, despite an equivalent existing, that they should get some type of break.

I’m not in the UK, so I can’t speak to their legislative process as specifically unfortunately.