The main legit. use I've seen is to advertise jobs for carers who are specifically male or female as they are needed for intimate personal care - otherwise specifying a role for females-only would be illegal. In practice it's more of a gender than a sex exemption - but the law struggles with social v biological.
Written by Cee R.
Writer, poet, (book) blogger @ dorareads.co.uk , Queer, weird, & a tad peculiar. Bookish rebel. Welsh as a tractor on the M4. Buy me a coffee @ ko-fi.com/ceearr