Historically, and happy to be proven wrong here, we've never seen a lab-leak of a novel virus cause a widespread outbreak. We have seen zoonotic transmission cause an epidemic/pandemic. So at least for me, I was working off of, "Is it likely that we're seeing something for the first time? Or is it likely this happened the way it's happened before?"
>>looper+(OP)
Depends on your definition of widespread. There have been level-4 leaks multiple times in the past. England had an outbreak from a level 4 lab in the past 20 years: