It’s not an exam, it’s a few boxes on a form. It would take an hour at best to do. The refusal to do so is the weird part. If he were to buy it personally would he also refuse to take the test?
You’re applying U.K./ Western logic to the politics of Gulf Royalty. As I said, he’s the de facto King of Saudi Arabia, sitting the test would be an insult and won’t happen.