All of the previous lab leaks were of known viruses that had previously spilled over into humans via natural processes, then were collected and later leaked out (again). I'm not aware of any truly novel viruses that spilled into humans through a lab leak. Are there any examples?
We can't truly know just how novel covid-19 is; we don't have sequences from the database of coronaviruses, and even if we did it might have leaked right after it was collected, without having been sequenced yet.
Is "novel" the right criteria here? If Covid didn't have asymptomatic/pre-symptomatic infectiousness, it'd still be novel but may not have become a pandemic. Therefor may not have even been noticed, no tests developed for it, etc...