I kindly disagree with you. Most of the platform provided by a console is nicely abstracted with SDKs. The code they touch is the SDK which provides direct, and tailored access to utilities and capabilities provided by the platform itself.
Even the Linux binaries of then AAA titles are ported by some talented developers, sometimes out of the studio.
I remember porting of Unreal Tournament to Linux was an official effort, but a work of a single guy.
So, I don't expect studio-wide POSIX knowledge on game studios.
macos? The same OS which decided no more 32bit binaries because of reasons? The same OS which decided no more opengl because of reasons? That OS?
No gamer uses that OS. If you think it's hard on linux, it's much harder on osx.
android is not posix, that is completely hidden from the developer.
chromeos is just linux + google tracking.
consoles are a complete separate world.
Please let's try to have a serious conversation. Game developers that use frameworks such as unreal are often unaware of how the underlying system works.
It happens, but there is an economic advantage in putting up with such breakages, while on GNU/Linux systems that money bag isn't there to keep game studios interested other than testing waters and running away afterwards.
Yet porting to GNU/Linux is not worthwhile.