Well, almost (49/51%).
Needless to say, the steam deck has definitely found its place playing Monster Hunter, Graveyard Keeper, and sometimes even Guild Wars 2 and factorio.
It does run Deep Rock Galactic and Vermintide 2 too, but I feel those are better played on the rig.
Euler diagram, since a Venn diagram needs to permit for all combinations, and as you point out, some don’t make sense.
https://en.wikipedia.org/wiki/Euler_diagram
You can run Windows on a Steam Deck. I don’t know why you would though.