someone who knows more can correct me, but if i'm not mistaken the game hasn't been approved for release in mainland china. the game is out in hong kong were the strict laws regarding games don't apply, so now that the localization is coming retailers in china are importing the game from hong kong. i may be totally off tho.
for a game on a platform that's not even officially available, and in a market where piracy is rampant, it's not too bad. also this is the number from 1 single distributor that supplies to 37 shops only. you could imagine the total number will be much higher.
Yeah quote from GI site:
Yesterday, it was confirmed that the Nintendo Switch has been approved for sale in the Chinese province of Guangdong through a Nintendo partnership with Tencent. This is the first time the console will be legally available in the country, though it is still unclear whether or not further Chinese government approval is needed or when the console might launch.