As far as I know, it only applies to Nanning of Guangxi province. However, don't rule out other cities of said province doing so too. Local recruiting agents will likely be aware of the actual situatiom on the ground there, where they operate, as will those in other areas of China.. But as always here, things can change suddenly, and even without any prior warning, as is mentioned on the Chinese Foreign Affairs Office website. They state there that they are under no obligation to provide advance warning of changes in visa regulations to visa applicants. And it has been known for individual visa offices and PSB's to interpret said regulations in a different way, seemingly arbitrarily in some instances!