I guess authors avoid using the word 'China' so their work isn't censored. They can write occassional bad stuff about 'Vermillion', which is a copy of China, but if they directly mention the name of their country, they'll probably get banned.
If man has to live underground for like 100 years or more, I wonder how mankind would look like years later. I mean, like feature wise cause we have to evovle in order to adapt in our surroundings. I wonder what's the difference hmmmm