No. They don't need to worry about defections. Unless the guy really wants condemn his whole extended family and next 7 generations into labor camps.
1. Every citizen will have ties or family to -think of- 2. The current regime (which is now on its third generation) will last 7 generations more. 3. You have any descendants at all
With this in mind-I am quite sure NK is selecting the people win a similar fashion. I would not be surprised if the punishment for defection is more sinuster than just not seeing their spouse/kids ever again.