Or are you in bad faith giving dubious priors?
"This lack of openness caused delays in efforts to control the epidemic, resulting in criticism of the People's Republic of China from the international community. China officially apologized for early slowness in dealing with the SARS epidemic."
https://en.wikipedia.org/wiki/Severe_acute_respiratory_syndr...
My experience in biology labs (though not virology labs) suggests that a leak of benign research is plausible, and that if it did happen odds are good that there wouldn't be a ton of documentation to suppress. Mistakes happen all the time, and if researchers filled out a report every time a tube was dropped or some PPE was ignored in a "pretty safe" scenario, there'd be almost no time for research.
I still think the total number of human-animal contacts outside the lab are at least an order of magnitude greater than inside of it, so I would rank the probabilities as (natural > benign research leak >> gain of function leak).