Part of the problem is that there is an enormous labor shortage in Southern China. The government has been pouring money to improve conditions in the rural parts of the country and as a result there are fewer workers migrating to the south for jobs. In Guangdong alone it is estimated that the worker shortage is in excess of 2m jobs. I am not familiar with Yunnan Province but in the satellite imagery you linked those apartment buildings you reference look like dormitories attached to industrial facilities. The labor shortage is preventing companies from expanding, or more explicitly they are consolidating in areas where competing factories are located. An example is Changan where I think every jewelry manufacturer in China is now located and it's increasingly congested as a result.