If your point is that the potential influx of HKers will create social tensions and feed into racism then I would agree, but that's not specific to the UK. Having 3M people suddenly popping up on your doorstep can be a challenge.
However, while I hope that many HKers take on the opportunity to get a real British passport, I know most will do this as a backup plan. They will funnel their families and finances out of HK (to the benefit of the UK) but still live in HK for the most part.
Most HKer know they can't just show-up in the UK and be successful there as they are in HK. Some will enjoy some opportunities and will manage to build or rebuild their success but most have their lives strongly anchored in the economic fabric of HK, and that's not easy to transpose elsewhere.