Especially anything that Mac Steam natively calls out lack of 32bit support has good support.
I previously played through Returns, Dragonfall, and part of Hong Kong on Mac before the 32bit-apocalypse.
This is speculation but I suspect there's something in that contract that prevents Valve from competing with Crossover on MacOS.
[1] https://github.com/ValveSoftware/Proton/commit/a84120449d817...