A zoonotic jump that happened to occur inside of a wildlife research facility due to bad lab technique is not that scary. If it's proven true, it's pretty likely that the lab operators will fix it. Could you imagine being the guy who caused the COVID-19 pandemic by forgetting to sanitize some tool? I bet whoever did it would be the single most careful and clean research scientist in the entire world after that kind of episode.
The bioweapon theory, however, is politically useful. If you want to start a war, or at least trade sanctions, a villain is a good place to start. Someone violating international law and gene splicing themselves a pandemic in a bottle is exactly the right kind of comic book supervillainy, without being technically impossible.