If you believe RaTG13 is genuine, then you should look past no where. At the same time (2012-2013), same place (TongGuan, Yunnan), some miners are infected by a virus with symptoms very similar to covid, and WIV was involved during the time and has the samples from the patients which have never been released.
All this is documented in a graduate thesis by a student from a local college in 2013.
The universities and labs in China usually subcontract the work a few levels down to some people who have no training or idea about what they are dealing with. And they would be more than happy to "recycle" whatever that can be "recycled", including dead experiment animals. For what is worth I had probably ate a frog I dissected from a school restaurant many years ago.
I think the lab origin is almost for sure. WIV released the RaTg13 sequence which is the closest to the covid virus. They had got samples from the patients who was infected by RaTg13 back in 2013. But they have never released the sequence, which could be a direct proof, or at least can bridge some gap.
All this is documented in a graduate thesis by a student from a local college in 2013.