As Jon thought, he realized that the stone was different from the swap. The stone makes everyone think the change is normal. But the swap... all that he asked for was to have the two people being swapped think it's normal.
He didn't ask for anything about anyone other than the two people.
So he didn't know how it would work. Would the stone make the two people and only the two people think it's normal? Or would the easiest way for the stone to do two people, be to do it to everyone anyway?
Jon was ready to ask the stone to find out, but someone outside had looked through the window, where they saw him standing. Well, their reaction to his pregnant condition would answer that question. It was....
