Wine is probably the best cross-distro Linux platform, especially for closed source products that don't get compiled for every specific repo. Flatpak/AppImage would also work but that lacks the raw system access that many games depend on (even if that system access is secretly emulated by Wine).
It could certainly be argued that I’m doing some mental gymnastics here, but I look at Proton/WINE as simply being part of the game engine. Traditional engines like Unity/Unreal have all kinds of translation layers and indirection.
Mostly it's an issue for video codecs in games (patents are the issue here), or games that use a less popular API. (From windows! Which has ~3 decades of APIs from multiple vendors. Let alone 10s (10-100 IDK) different ways of playing back audio or a video, or both at the same time.)
Some of the changes are simply more bleeding edge patches or game specific tweaks that are included faster than official releases include them.
Also, it's probably a joke.
Apps like Lutris, Spotify Yuzu are on the Discover app store which uses flatpak. Flatpak is on many distros already installed or can be installed manually.
(PS: The Steam Deck's OS isn't even Arch Linux. It's based on it and uses Arch packages, but updates come from Valve through their own update mechanism with a read only file system. It's like calling Ubuntu Debian just because Ubuntu pulls packages from Debian Testing.)