I've never really thought about whether the game looks the same using its Windows vs Linux renderer. I installed HL2 to check out the anniversary update and decided to try the Windows renderer on Proton. Would you look at this difference... Linux is the top one, Windows is the bottom:
Is this is a thing? Have you tried other games and seen the Windows version looking better?
Sadly for many games the Windows version runs and looks better than the Linux version. That's often because the Linux version is done by outside contractors whose contract expired. So while the Windows version will receive updates the Linux version lies stagnant.
See Tomb Raider 2013 for instance. The Windows version via Proton looks and runs much better than the native one.
Once you get a devops pipeline set up, you do all versions at the same time and have the compiler farm handle it. No reason the native versions shouldn't be receiving updates at the same time when its become rather easy to integrate multiple targets at the same time.