[1]: <https://github.com/FWGS/xash3d-fwgs/blob/f0342763547d9bcf486...>
You're right! It looks like Linux has a native build too. Apparently the Windows version, through Proton, runs better though (not that it matters).
The Linux and Mac ports happened in 2013 or so (presumably getting one working went a lot of the way to getting the other working, though there is some speculation that Apple poured in some money to help make it happen).
Later it became clear why: the Apple Silicon transition, and Rosetta 2, which is optimised for running x86-64 binaries on Apple's Arm64.
But the same change is looming on Linux: Ubuntu tried in 2019 but was persuaded not to, Fedora has tried more than once.
WINE 11 can run Win32 binaries on a pure 64-bit host OS without 32-bit libraries. So, you can run some 32-bit Windows games on 64-bit Linux and macOS which cannot run the 32-bit binaries of their own older versions.
Apple merely jumped first. I think it's not to be blamed here. It'll happen everywhere in time.
EDIT: this was for HL1 I’m not sure about HL2