Concretely what are you imagining here? US/WHO/UN says "there was a covert bioweapons program" and China says "no there isn't" and then... we invade? We embargo China?
The CCP would lose face, which is one of the worst fates for them. No more mandate from the heavens. Sure, they could try to deny it and claim the world is jealous of China or something like that, but that's unlikely to work for very long, especially with the rest of the planet. Losing their mandate from the heavens to rule China could very well lead to their ouster and perhaps the balkanization of China. Losing the respect of the rest of the world at a time when China wants to be the other major superpower, would be disastrous for them. In a multipolar world, the superpowers compete against each other for the loyalty of the rest of the world. Hard to do that when every single country on the planet suffered during the pandemic.
Lose face in the eyes of whom? Not clear to me that "this came out of our advanced bio research lab" is more damning than "this came out of our extremely unhygienic wet markets in urban centers."
These things move slowly and by little bits over time. If there were to be found a covert bio weapons program it costs China some credibility, not much but a bit and over time it just keeps happening.
