Even your link says "one country" :)

The key was "two systems" which I think is the more relevant part to the article ;)

They've reneged on many aspects of that since handover.

Granted, but put quite simply, I have residency in HK but still need a visa to visit mainland China.

Also the capital controls are entirely different. It's naive to say they are the same country when they are demonstrably different in terms of culture and laws - despite their many similarities.