While I agree that more extensive tests would be interesting, there are quite a few inaccuracies in your argument that make me disagree with your conclusion.

Firstly, Steam’s shader pre-caching does not work like that. There are no “good enough” defaults being generated every day. The caches you may receive have been generated and uploaded by other players with the same compatible system configuration (I think GPU and driver version, but there might be other factors I’m not aware of). So you only receive shader caches when someone else with a compatible system has uploaded them already. Furthermore, these caches aren’t necessarily complete. As games often compile shaders on the fly and not everyone plays every bit of content in every game, local compilation still happens pretty regularly.

Secondly, shader compilation is by no means limited to the first launch of the game. When the game itself doesn’t have a dedicated (and comprehensive) shader compilation step at startup, shaders may have to be compiled every time you access content in a game that you haven’t seen before. Sure, this is most noticeable at the start of the game, but it might also happen when the final boss enters its sparkly third phase, punching your stuttering, shader-compiling butt into the next wall (which might also require further shader compilation).

Lastly, I disagree with the general assessment that these advantages are somehow invalid because they might be limited to shader compilation stutters. When I download a new game, I want it to run properly. The shared precompiled shaders are a great solution for a bunch of stuttering, and they are only available on Linux because they actually require the compatibility layers. Microsoft hasn’t implemented something similar for their new shiny handheld. So I think it’s absolutely legitimate to call them out on their unoptimized device. I think, for the end user, it’s really just semantics to discuss whether the issue at its core exists because of Linux or because of Windows or because of caching or because of some unknown deity who just really likes Gaben. The fact is: from the data we have so far, it looks like Bazzite is a better experience on a handheld Microsoft co-developed when compared to Windows. And that’s both very sad (because I’d really like to have some serious Steam Deck competition) and really funny (because seeing a very big corporation’s gaming division fumble everything they do makes me giggle).

… Also, Wine is not an emulator, but I think you know that. ;)

I don’t think Kingdom Come: Deliverance 2 has a native Linux version, so yes, these results are achieved using Proton.

This is both a remarkable achievement for Valve, CodeWeavers, and everyone involved with the development of these compatibility tools, as well as a pretty damning showcase of Windows’ performance, even when configured as a somewhat debloated special handheld version.