When attempting to make a trade for a resource nobody has, you get a message saying nobody has that resource, and it prevents you from offering the trade. However, if you are the only player with that resource, it let’s you make the offer, even though no opponent has the resource to accept it. When offering a trade for a resource that no opponents have, regardless whether you have that resource or not, it should prevent the offer being made with the message ‘no player has the resource to trade’.
Ita a feature not a bug, players shouldnt receive that information, especially as fishing for information for monos is a knkwn tactic