it is to keep his health secret.
The reason? They are protecting against a literal info dump. "The leader's excretions contain information about his health status so they can't be left behind," Lee Yun-keol explained.
There were a few news stories horrified that a soldier who had defected from North Korea had lots of parasites, so presumably Kim doesn't want you to check if he has them too.
and by the way: What's the story behind cute pooh?
Have you seen these cute poop toys around Korea yet? Well apparently if you dream of poop it is a sign of good luck. This is because in the olden times farmers used to use poop as a fertilizer which results to better harvest. Therefore similarly by dreaming about poop it means there will be better harvest of good fortune! And these toys are so damn cute!