That is Wikipedia. Now, please compare to what the actual British government says:
"Rights as a British national (overseas)
are subject to immigration controls and do not have the automatic right to live or work in the UK"
So, 2nd class citizens, with definitely no right to relocate to the UK. That's compared to Macau, where Portugal did give real, regular, Schengen passports before leaving.
I know that from having been to Hong Kong and met actual Hong Kong people, many of which are careful to hold onto their Portuguese passport obtained through family connections to Macau. The BNO passports are worthless.
As for the law, it was last used in 1967, and HK went back to China in 1997. So the argument "it had not been used for so long" does not hold water. When the UK was in charge, it definitely was not so long ago. Since you are able to remember the Tian'anmen events of 1989 today, they could very well remember the 1967 riots at that point.
And the part about not establishing democracy? What's the excuse, also forgot about it because it had been so long?