It's not that the loss of seven million lives doesn't matter. It's that because it's already happened and both things are plausible, to prevent future calamities like this we need to address both possible sources.

If it turns out it was a lab leak this time and we crack down on lab safety but fail to get zoonotic transfer better under control, we are still liable to have millions more dead sooner or later. Same thing if vice versa.

That's the sense in which it doesn't matter: for the future, we need to act as if both origins are true.