I am not too sure of an embedded social malaise in Yunnan unless you are referencing the numerous indigenous peoples or 民族。 It is true that China has encouraged or caused migrations of Han to remote areas for a variety of political and social reasons. My feeling is that Han perceptions of 民族, other races, cultures and nationalities tends to be developed from the superior position. True or not, I feel the issue is not of malaise but of money and statistics.
Development, East, West, or wherever is driven by finance. The government was slow to encourage Western development because the West is, well, far from home and often occupied by lazy, uneducated other people. Once the coastal areas became developed the costs of continuing to use increasingly scarce coastal resources and migrant labor, someone reached the conclusion that there was a huge amount of cheap land and cheaper labor to be had in the West. The money, however, was slow to come. Perhaps the splitist movements in Tibet and Xin Jiang provided the clarion call, or, maybe it was that some accounting calculations were made, or, the realization that the yuan input-to-output ratio was better, or... who knows. The march to the West began.
Oil refineries and chemical plants are not highly labor intensive. The number of jobs for the investment is low. It is true the labor needs to be higher skilled but often, as in the case of rat for sheep, that can be avoided.
What is true, is that oil refineries and chemical plants have a higher potential for pollution, deadly pollution, than other types of industries. So far, over the last 30 years, the government has not demonstrated leadership or the ability to act in addressing the growing pollution crisis in China. Originally, pollution was considered one of the costs of development and routinely dismissed as 'we can't help it'. Actually, pollution has only two causes; ignorance or greed. Some pollution occurs because of a lack of education or knowledge and this produces unfortunate results. But most pollution is the result of economic decisions made to economize or avoid costs. Leaders, in both SOE and SME enterprises, will avoid investing in pollution abatement as the investment, operating costs, and disposal costs are considered 'avoidable.' Any vague possible problem 10 to 20 years in the future just can't get in the way of today's rewards.
An oil refinery or a chemical plant is a high ticket item. These fall into the investment part of GDP calculations. They also have an economic value, a few jobs, yes, but clearly economically viable. Build a few plants and you get the GDP hit. Operate them and repay the loans, add to yearly GDP, and all is well.
A waste water treatment plant is relatively low cost, takes a lot of land, and requires never ending operating costs. The GDP impact falls way behind building a 30 floor apartment building on the same bit of land then dumping waste water into Dianchi. Not an attractive investment, water treatment is a shitty business to boot.