What Hong Kong does and what it should be doing are completely separate issues.
To me, it's pretty clear the Government is not basing its actions on epidemiology. Else how could it justify banning visitors from Taiwan? Or quarantining residents returning from Taiwan? Is there a genuine risk when the situation there is so much more favourable than the situation in Hong Kong?
Not to suggest I know how the Government is instead making its decisions. I've a suspicion, though, that the approach is simply to avoid making decisions, which leaves us gummed up right where we are for who knows how long.