Of course Jon could simply Know if he wanted to, but he is opting out of it, which isn't always easy. However, Tony's hesitation is a clear indication that something was off and Jon doesn't have to prod or guess to receive an answer regardless of Tony's silence. A silence Jon joins in on for a moment while understanding sets in.

"Tony..." Jon starts and reaches up once again to replicate the motion Tony had just taught him and flip the faceplace back open while he staps forward, a concerned frown on his face. "Why?" And this time he doesn't want images to be the answer.