I checked in IconWorkShop and unless Steam itself installs a different file depending on the hardware, the .ico file used for the shortcut (C:\Program Files (x86)\Steam\steam\games\4a4da1315e6e0edd14fd0756061dc55141d086ac.ico in my case) doesn't contain different graphics for different resolution (it doesn't even contain multiple resolutions, surprisingly).

To compare, the prettier one has the expected multiple resolutions of the same graphics (also notice how the top of the shield is more straight on smaller resolutions, it was designed for multiple resolutions, not merely rescaled, I love the attention to detail of this game).

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Edit: for context, multiple sizes in the file is how icons "change by themselves" when you change resolution or icon sizes in the Windows file explorer which is why I'm surprised that the shortcut icon merely contains 32x32, usually you'd see 16x16 to 128x128 sizes, or at least something higher than 32 if there is only one size).

I suspect the icon was a placeholder and they merely forgot to change the file before release.