Small sample set aside, the performance differences here are much bigger than I've seen in previous linux comparisons. Something has to be off right? Curious if anyone is able to reproduce these results.
It's running through Proton, he mentioned that in the benchmarks it shows up "as playing on windows" because of Proton.
Other than that Nick is pretty transparent about what he does, if something is not mentioned it's likely whatever is default on the distro when running steam through flatpak (flatpak was mentioned).