Oh, I'm certain that after we explain it to him he'll understand. [ at least, Strange hopes that after it's explained to the Prince he'll understand. ] But again, this is all about us being on our best behavior and part of that consists of leaving a good first impression.

I know you can't eat or drink, but he doesn't. And the likelihood that it's explained to the Prince before we eat or drink is slim. As such, he'll most likely think you're being rude.