If it was by accident, then it calls into question the quality controls over labs. It isn't "equally likely to happen anywhere" if the quality and safety standards vary by location. Operating a lab with poor safety standards is not "bad luck".
China has ways to stop this class of research internally. It's very likely to happen. That's the entire point.
China does not need to admit, discuss, have referendums, or partake in any other self-harming activities.