At the end of the day the only people who most likely know whether it was a lab leak or not are the chinese authorities. So we will likely know in 50 or 60 years if those archives are made public (like for the Katyn massacre). The CIA/NSA can possibly get its hand on incriminating communications, but who is going to trust those guys?
Also I wouldn’t be surprised to learn that the chinese authorities got all covid lab samples destroyed without being analysed. The best way to not leak that you may be responsible is to ensure no one, even yourself, can ever know whether you were responsible.