

you just need to right-click on the game (in the left panel), go to Properties -> Compatibility, and set it to Proton Experimental
You can also enable it for all available games from Settings > Compatibility (and you’ll still be able to override the version on a per-game basis as well)
I can’t cite a specific source since I was researching the subject for a fantasy novel I was writing at the time, and I’m not even sure the material I was reading was in English, but I remember the author was making a comparison to Roman legionnaires throwing their Pila synchronously to maximise their impact/psychological effect. And it made sense to me since every soldier only had two to carry.
Apparently shooting them in single massive salvos would force their enemies to crowd into one another (they’d have to push someone else into the path of a Pila to avoid one that’s coming at them) which devastated their morale.