A Bayesian Approach
In cases like this, I tend to simply say "I don't know", and leave it at that.
I think that's better than coming up with any kind of number, which is then all too likely to take on a life of its own, and persist in spite of any additional relevant data that may appear.
Fortunately, I don't have any decisions to make that would benefit from being partly based on this answer.
See also: <https://www.rootclaim.com/analysis/What-is-the-source-of-COVID-19-SARS-CoV-2> for a similar analysis
What Dino said. People will choose the numbers they want to get the conclusion they want. Just because you have equations doesn't make it any more "rational."
It might be that scientists don't want to believe their research killed so many. But I think it is more that everyone who is thoughtful realized that, at the time, saying "lab leak" would unleash violence against Asian people around the world.