That being said I disagree. the CCP going as far as chaining/nailing doors seems more than excessive (remember that officially there has been about 5000 deaths from covid in China) and not as esaily explainable as you suggest.
The explanations you give make sense but they wouldn't be unique to China. A lot of authoriatian countries share the same concerns and want to show they have things under control and to save face. Yet no other country went as far as china did. When you add together the fact that the virus originated from China, that a lab leak can't be completely excluded and that there response to it is unique and seems irrational , I can't blame people for having a bad gut feeling about it. It doesn't mean that the suspicions of the people that find it fishy are founded, just that them feeling that way is somewhat understandable.