I have "done a little research".

I appreciate you citing and quoting sources that proves my point. Again, when you literally said you would be trying to end ALL life on Earth, it implies full extinction, not just "most of life on Earth eventually dies, but not all".

Nobody is dismissing nuclear war as not a big deal. There's absolutely nothing in my comment that even implies such. But like you said,

This implies that some humans would survive, eventually to repopulate the planet, and that a species-level extinction of Homo sapiens is unlikely even after a full-scale nuclear war. But the vast majority of the human population would suffer extremely unpleasant deaths from burns, radiation and starvation, and human civilization would likely collapse entirely. Survivors would eke out a living on a devastated, barren planet.

And this is assuming one of the worst models is correct. This isn't a semantic disagreement, it's a very tangible difference than what you said.

Society and all of the production capabilities that come with the industries inside of it would collapse-- it would be an apocalyptic event, but I've yet to see any evidence that it would an an extinction one, or even that it could be an extinction event that ends our species.

Previous models I've read have the immediate death count being at around 10% of the planet's population in the event of a nuclear war (I believe it being with the nuclear weapons held by the US, Russia, and China) with 50 to 70% likely being the number that dies in the aftermath-- mostly concentrated on the northern hemisphere. However, I'm having trouble finding an .edu or a .gov source that goes into detail about the death counts resulting from the aftermath of a nuclear war.

Even if only like 5 to 10% survive though, that's still a far cry away from "100% ensured that all life will end"