Why do they say that the wall was started and finished in the Qin dynasty. it was in the Ming?

MJ, it's true that Emperor Qinshihuang of the Qin Dynasty order to build the wall. However, the emperors of later dynasties, such as Han and Ming Dynasties also built the wall. However, the walls built during Qin and Han Dynasties almost disappear. Today, we can just find the ruins. The intact wall we saw today were mainly buit during the Ming Dynasty.

the Qin added defenses to the wall