Windows also does not have 100% compatibility. Try playing something like age of wonders 1 on current windows. I could run in out of the box on steam deck but not on my pc that at the time had windows 10. I think Windows no longer has compatibility with win 98 and lower but i might be misremembering.
Linux must achieve 100% compatibility. Otherwise the doubters will not shut up.
Windows also does not have 100% compatibility. Try playing something like age of wonders 1 on current windows. I could run in out of the box on steam deck but not on my pc that at the time had windows 10. I think Windows no longer has compatibility with win 98 and lower but i might be misremembering.