My guess is that this is legitimate, but a strategy like the Republicans used in Northern Ireland. Everyone knows that your little city can't defeat the PLA. What you can do is make yourself ungovernable without making China do things that would tarnish their world reputation. If China quells this protest, but in the process turns Hong Kong into another Xinjiang (including the "reeducation" camps for protesters, and the invasive surveillance on the rest of them, most of whom were alive during British rule), all in violation of the treaty with the UK, then they lose.