This is not a good thing btw. Any unused anonymous page takes up space that could instead be used for file-backed pages that make your system faster.

Can you expand here. I think my attempt at brevity in this part wasn't helpful.

Swap is not tiered storage!

I meant tiered with priorities only, yes.

Cool tech but it’s dead and was quite niche even when it was alive.

We are not talking about the original purpose of Optane as supported on Windows. It's just a (perhaps somewhat outdated) example of a storage device "smaller but faster than your average SSD storage", which is very much not did tech.

Not a thing you actually want to use for swap

Depends on the use-case. But yes, this can also be used as the fastest disk tier/priority of normal swap devices, which is why I mentioned both.

This makes no sense at all unless you are extremely space-constrained on the NVMe and absolutely must not OOM – even if progress stalls to an absolute crawl.

Why would you want to see killed processes when you go back to your workstation, in the 1/10000th scenario where something runs amok pushing memory usage to unexpected high levels? When you can simply investigate the reason behind the rare occurrence, then move all the pages off the slowest devices immediately with swapoff?