While this wish occurred within the range of the Skull, Jon and Karyn didn't hear it. So neither found anything odd at all when Jon suddenly filled out his cute top with a perfect set of C cups.
So now we have Jon, a normal teenage boy, with a gorgeous set of breasts that he and everyone else thinks he's supposed to have.
No one notices that his waist is slimmer, or that his arms and hands are delicate and feminine. Or rather, no one notices that it's unusual.