Mr Douglas and Mrs Zeta-Jones is according to Wikidata: "actor / actress". When you look at the picture it is obvious; one is an actor and the other is an actress.
Wikidata knows enough about Mr Douglas and Mrs Zeta-Jones to infer how to label them. One is known as a "male", the other as a "female".
To enable Wikidata to infer labels that are determined by gender, labels need their own statements. The MediaWiki software has the functionality to deal with gender; it is just a matter of applying this logic.