Any economic activity draining away has limits defined by role: Beijing as a region is a scary, massively regulated trading partner that isn’t afraid to rip the rug out from under anyone, and has a really crap reputation to boot.
HK, however, is less regulated, much more pragmatic and has an excellent port.
If you need a better comparison: HK moves the washing machines, computer parts and has agreements all over to prevent piracy and high tariffs.
Shanghai moves the oil, the chemistry, 99 cent knick knacks and toys, and people.
