You don't have to say anything about his "gender identity" to enforce a professional dress code

In a sane world, this is true. But in woke Tranada (where men get to define what a woman is), this guy gets treated the same as a woman with naturally large breasts or a beast cancer survivor who wears a slightly padded bra.

Also, if you tell him mini skirts are against the dress code, he can just cry that mini skirts are the only things that cure his dysphoria and he'll literally kill himself if he can't wear them to work

He doesn't get treated the same as a woman. A woman wouldn't be allowed to work dressed like that.

He gets treated like a man. This is the definition of male privilege