there's nothing legally preventing mainland-Chinese from choosing to live in HK This is completely wrong. Mainland-Chinese may only move to Hong Kong to reuni

there's nothing legally preventing mainland-Chinese from choosing to live in HK This is completely wrong. Mainland-Chinese may only move to Hong Kong to reunite with family, and they have to apply for a One-Way Permit, which has a "quota of 150 people per day and the waiting time for spouses is currently 4 years": https://en.wikipedia.org/wiki/People%27s_Republic_of_China_Permit_for_Proceeding_to_Hong_Kong_and_Macao https://en.wikipedia.org/wiki/People%27s_Republic_of_China_P... To even visit Hong Kong requires applying for an Entry-Exit Permit in person, and duration is typically limited to 7 days: https://en.wikipedia.org/wiki/Exit-Entry_Permit_for_Travelling_to_and_from_Hong_Kong_and_Macau https://en.wikipedia.org/wiki/Exit-Entry_Permit_for_Travelli...