I don't see any evidence for the speculation it was lab created (or modified into it's current form) except for an acknowledgement that the capability to do so exists.
I don't doubt the possibility of such a thing occurring, but I just haven't seen any evidence to support this.
It goes quite deep into the genetic analysis of SARS-CoV-2 relative to existing bat coronaviruses, laying out the case that it is definitely of a non-natural origin.
I am not anywhere near knowledgeable enough to fully evaluate the claims, but I would really enjoy seeing a rebuttal that is as clearly written to make the case for a natural cause. To me the Nature article just says 'nah, evolution is random, therefore SARS-CoV-2 randomly happened.' but it would be nice to see more detail. Especially with the closest ancestor of RaTG13 being decades of evolution away. (not to mention the questions around the origin of RaTG13 on the author's site...)
I don't doubt the possibility of such a thing occurring, but I just haven't seen any evidence to support this.