Most likely the police didn't specify because most if not all police forces are captured by gender ideology. Previously they would have referred to Herbert as a "woman" and 'she", and defended that action as respecting the person's chosen identity - see for instance Scarlett Blake (murderer) and Naomi O'Brien (child sex offender).
This attracted some criticism, so now the police will often avoid referring to sex or using pronouns altogether in statements about transgender people.
You will have noticed that the police statements about the two men arrested in the investigation into Ann Widdecombe's murder (one later released without charge) referred to the sex, ethnicity and nationality of the arrested persons, "white British man".