It’s a crime if it’s being used to physically attack the cop.
Incidentally if he posted about a riot in our city (thankfully pretty much unheard of) he'd be carrying out exactly the same function as this app!
Following US procedures in HK does not make sense. Companies always obey local laws but not laws in another country.
After that, the next question is if Apple, which even kinda positions itself as the new "Don't be evil" company including fighting some governments e.g. when they get told to subvert their own security tech, should side with such draconian laws or with the app makers.