What Jon didn't know was that the stone couldn't take anyone's lives. Jon's wish for women to be born only from multiple pregnancies made female births much more numerous and so the world's population had to reflect the higher female/male ratio. The stone couldn't kill anyone so many men were transformed into women.
Jon being one of them. He was about to become one of a group of quintuplets. He was also the only person on the planet to actually realize that something have changed. How will he handle his new life with no recollection of it?