“en_US” is “American English”, not “English on a Phone in america”. The alternative “zh-*” codes are SG, TW, or HK. It’s checking if the user has their region set to “Mainland Chinese”, not That their phone is “Chinese on a phone in China”.
Actually, american english is "en-US", "en_US" means english with the region set to the US, at least on iOS. But yes, it is checking that their region is set to mainland china.
