The border between China and NK is not hermetical closed. It's the easiest place to penetrate the border if you want to flee the county. Also China is NK's larg

The border between China and NK is not hermetical closed. It's the easiest place to penetrate the border if you want to flee the county. Also China is NK's largest trading partner and the largest employer of NK labour outside of NK (buyer of slave labour might be more precise). So it's really not so far-fetched that people living on the Chinese side of the border meet north koreans and hear their stories.