Now maybe statistically it's more likely that someone just happened to have a heart attack next to an open bottle of poison, but Occam's Razor isn't to select the most likely answer, it's to select the simplest answer. The simpler answer is that he ingested poison, rather than he had a heart attack near a bottle of open poison.
If a pandemic involving a bat-virus swapping species starts in a city then it was probably just a virus jumping species. If that city happens to be doing active research on how much bat-viruses can swap species, then I think Occam's Razor can apply.
Obviously there is no objective truth to Occam's Razor, and what I think is the simplest explanation may differ from what you think is the simplest explanation.
Also, I think doing active research on something that can jump species and is highly contagious in a city would massively increase your risk of it jumping species in that city. That risk is increased if the lab is known for poor controls and was flagged as a risk, as the one in Wuhan was in the us cables.
Additionally if a researcher did get infected, there is a high chance that they would be asymptomatic and wouldn’t even know it was them.
The only “proof” that it wasn’t from the lab is the dna analysis, but that only proves that the research wasn’t altering the genome / that there was bio-engineering, there is still loads of research you can do without playing with the genome.
Looking at the behavior of the virus and the arguments of some evolutionary geneticists (and I'm not well versed in genetics so I'm trusting their credentials here) changes things a bit of course.