Nope, you might have heard wrong. In China, legal age to be married for women is 20 years of age, not a day younger. But men must be at least 22 years of age.
It is a well known fact that corrupted officials are very abundant in China, and I agree that it is easier and cheaper to get what you want done in the countryside than in the city. Bribes and guangxi is still very popular in small villages in China, but is it worth it?. Especially if you live in China ?. What would happen if you are caught ?
And since you, as a foreigner, can only ne married at the Marriage Bureau of the city, town or village where your future wife's huckou book is registered, what if is not at countryside?.
I had a friend who registered a gas motorcycle (real big engine) with a 3,000 Rmb bribe to a village chief, and got a real driver's license too besides the plates. But it lasted until the Police in Nanning caught him up and confiscated his motorcycle.