But cross species transmission is known for quite a lot of pathogens. Ebola is a recent example. Asserting it is so unlikely as to be dismissed out of hand doesn’t match knowledge in the field.
It happens, especially between closely related species, in both genetic and physical proximity, like monkeys and humans, but it’s rarer between further apart groups. More importantly, it follows patterns (first a few opportunistic infections, then more common ones, then transmission between new hosts) that were not observed with Sars-Cov-2. Hemorrhagic fevers were occasionally described among bushmeat hunters before Ebola became endemic. There were effort to discourage the practice precisely because of a fear of future contamination beyond that small group.
I’m not dismissing that it happen —I can’t imagine you’ve read anything like that in my comment— but the natural origin theory changes our understanding of how fast it can happen.
