The WIV has BSL-4, BSL-3 and BSL-2 labs. But the research involving insertion of human specific furin cleavage sites into coronaviruses sampled in the wild was done in BSL2 which just means a thin medical mask and gloves. https://theintercept.com/2021/09/23/coronavirus-research-gra...
> Infectious material used in procedures with a potential for creating aerosols or splashes, or used in high concentrations or large volumes, must be handled in an annually certified biosafety cabinet.
Realistically, many people's bayesian priors are severely skewed against the lab leak hypothesis because it is associated with Donald Trump, and even intelligent people find it difficult to separate the message from the messenger.