It's definitely a variant of the 'saving face' theory 1). Here are several factors that play in:
  1. China's urban areas are the highest density human populations on the planet. In particular in Guangdong and on the east coast.
  2. The SARS epidemic was very traumatic in some pockets. It was like a much shorter but more potent health scare with similar effects. A bit related to the above.
  3. China's government is sometimes perceived as uber-efficient and effective in the West. That's only half-true, at very best. It can also be comically ineffective; so much of what bureaucrats do is to satisfy what their superiors seem to demand; so often what is actually required is extremely obtuse. There are communication problems because speech is not free, even at the deep level (what a middle manager can say to a boss; what a local party official can say to a high ranking CCP member). Lack of that flow of information leads to really bad outcomes, often.
  4. Xi Jinping is really very authoritarian, and seems from what I can tell to have very rigid ideas about things. Once he had decided what his COVID19 policy was, you can imagine (see 3) how hard it would be to change it. (The CCP, anyway, is all about top-down control, it's like its DNA .. to a hammer everything is a nail; a biological disease in the society is treated like a mind-disease (people having 'wrongthink') - stamped out with extreme prejudice. Unfortunately this is a ridiculously impractical idea, but see the previous point).
  5. Don't underestimate how stupid humans are in groups :)
Re: 2) sure it could well be from that lab, I'd say far more likely than not at this stage, but no way there's some hidden effect (just my guess of course).
Re: 3) Can't see that being even a little bit plausible tbh