The actual job ad you're on about is on the link below. Apparently, Changchun is one of those outposts of China where the visa regulations are not followed to the letter by the powers that be in certain circumstances.
That's a good thing for those of us who are short of the required academic teaching qualifications or officially too old or too young to be employed as foreign teachers in China, or indeed without the necessary two years of valid teaching experience.

http://jobs.echinacities.com/showjob-106617.html