I think Chinese vaccine wasn't very effective and they were able to contain early infections so the "survivors" immunity isn't widespread. In these conditions the consequences of a COVID wave could be quite severe, depending on which strain they're getting. Like the first wave e.g. in Italy.

I think they're fucked either way, lockdown or no lockdown. But the rationale for the lockdown could be to avoid overwhelming the hospitals. Implemented in a typical for China totalitarian fashion. I've seen reports they're exterminating pets.