~Unfortunately, I cannot reproduce this issue any longer - after removing Steam from my home, it's prefixes and what I knew could potentially be holding old files that haven't been updated... I re-installed my system and...
I tested this in my laptop, it works correctly. I've tried deleting my prefix, Proton's prefix and the game files... Not sure where to go from here as it might not be an issue with Proton but instead the packaging of Ste...