Honest question: if this is common knowledge of people in the field, why wouldn't people genetically engineering a virus (and trying to hide it) do so in a fashion to make it look more like evolution in the genomes? Is that not possible to do?
On top of that, there's no reason to do it for a military weapon. For military use you don't infect a few people and hope it spreads, you infect a whole bunch and hope the whole thing spreads quickly enough that the virus can't be stopped, and it overwhelms an entire population by incapacitating or killing them.
Dispersing virus over a significant fraction of a population isn't easy or quiet, so whether it's a natural disease or GMO doesn't matter, because they'll know who did it.
The only scenario in which it makes sense to evolve a genetically engineered weapon in a way that hides its origins is for bioterrorism... and bioterrorism is very rare because it's a lot harder technically than terrorism that consists of shooting up a military base or running an exploding motorboat into a ship.
How can you say this as fact when we don't even know the morbidity rate of the coronavirus? The story isn't over yet, but it looks like it could be twice as deadly as influenza.