The practical difference is that many of the arguments against lab-leak theories in general are actually arguments against the gain-of-function theory in particular. Things like lack of markers that would indicate engineering, or the presence of markers that would indicate animal origins. So distinguishing the two candidate theories becomes important for discerning whether the evidence is for or against a lab leak: you can't use animal-origins evidence as evidence against a lab leak, only evidence against an engineered virus.

Intentionally seeking out potentially harmful natural pathogens from remote locations and placing them in close proximity to people isn't relevant to lab leaks? Then why are they studied under high levels of security in the first place?

GoF research is so obviously a bad idea. The risks are enormous and the rewards are minuscule. But lab leaks of natural viruses are indicative of problems too.

One way to look at the difference is that a "natural Ebola" almost certainly would have spread at some point anyways, and so it wouldn't affect the total number of world deaths in the end, just make them happen some number of years sooner.

Whereas an "artificial Ebola" would never have existed without it being intentionally created, so all the deaths aren't just time-shifted, they wouldn't have happened otherwise. They're new.

> a "natural Ebola" almost certainly would have spread at some point anyways

Plenty of plagues have evolved in the last thousand years. That doesn’t mean they, or their deaths, were inevitable.

I think the natural-virus-leaked-by-lab theory hinges on the argument that, (assuming it was true, then) had the lab leak not have happened, SARS-CoV-2 wouldn't have made to jump to human by itself. And this is where the Ebola analogy breaks down. Because SARS-CoV-2 has a higher basic reproduction number than Ebola, meaning it's more transmissible. And it's also much less deadly than Ebola, meaning it has much more opportunities to spread.

Remember, it is a virus that caused a global pandemic, despite all the efforts made to stop it. Based on that, I think it is highly likely that whether the lab leaked it or not, it would have made its way to humans by itself. In other words, there would effectively be no way to tell one scenario from the other.

It guides policy. If it was engineered, it means this is research we really shouldn't be doing. If it was a wild virus being researched, it means we need to take the threat of spillover more seriously.

the "practical difference" is that zoonotic spillover and lab leak may not be mutually exclusive theories.