The term 'tu' referring to the hill tribes was an insult meaning they were backward. How has the meaning of 'tu' changed in the chapter A Drinkable Antique?

The term 'tu' has changed in the chapter A Drinkable Antique to mean untouched by the evils of civilization. Many people who live in the city would like to visit Yunnan because it is quiet and peaceful and has fresh air.