While "no closer virus to SARS-CoV-2 than RaTG13 exists in the wild" is falsifiable, the problem with this approach is threefold:

1. Absence of evidence is not evidence of absence, so if no such virus is ever found, it doesn't prove anything.

2. Could we prove some closer virus to SARS-CoV-2 had, itself, not been lab manufactured, or would the same conspiracy theorists posit that, too, had been engineered or created through gain of function research?

3. Would conspiracy theorists, even if they believe such a virus were natural, believe that it is "close enough" to SARS-CoV-2, or would they say it is still too different to prove a link?