If I get it right (from what you said), HK government never tried to discriminate people based on if they are from Mainland China or not, albeit there is obvious discrimination and bias among public for different reasons(not the focus here). While CCP government openly, in policy, discriminate Chinese from within mainland China, and contrary to most countries or regions where the discrimination is to protect or in favor of the locals, the one enforced by the Chinese government is to discriminate against the locals. This is also not very deviated from what mainland Chinese sees themselves: self < people from HK<Japan<Whites