It's the game of wits from Princess Bride. They might want to take someone out, so you can't choose the wine in front of you. But, they must know you know that,

It's the game of wits from Princess Bride. They might want to take someone out, so you can't choose the wine in front of you. But, they must know you know that, so you can't choose the wine in front of them. But they may be trying to protect their image, and if so, you can't choose the wine in front of them either.