Also known as, you don't know technically anything about Windows.
There is a very big difference between supporting UNIX, and Linux kernel syscalls ABI on top of pico processes, the technology from Drawbridge kernel taken out from Microsoft Research, which incidentally is also used to port MS SQL Server into GNU/Linux.
As for the rest I could provide examples of how the BSDs and Solaris failed in similar attempts to clone Linux syscalls table, despite being UNIX, before Microsoft's attempt, but who cares?
> As for the rest I could provide examples of how the BSDs and Solaris failed in similar attempts to clone Linux syscalls table, despite being UNIX, before Microsoft's attempt, but who cares?
the BSD approach is still supported and part of FreeBSD, so presumably someone cares about that
While the original support wasn't great, SUA was quite usable, until they decided to discontinue it on Windows Vista.
Nowadays we have WSL, which makes more sense, given how many folks buy Apple hardware and then complain UNIX isn't GNU/Linux.