The latest border closing measures are practically useless as far as getting on top of the coronavirus spreading situation is concerned. All it will do is reduce the volume of Hong Kong - China traveller volume by a bit, but all remaining travellers will simply be consolidated to those 3 remaining ports of entry.
Furthemore, the airport and Shenzhen Bay entry points are the highest volume ports of entry for Mainland Chinese visitors anyway, so little is changed.
The way Carrie Lam is handling this is exactly like how she absolutely fxxked up the China extradition law fiasco. At first it was steadfast refusal, then she gave in a little, calling it postponement instead of outright withdrawl, then she gave in a little more, saying the bill is dead, and then she uttered some more nonsense while still refusing to formally withdraw it. Just like the CCP hasn't learned shxt from 2003 SARS, Carrie hasn't fxxking learned shxt from the extradition bill either.