Alt text: meme with the 'Always has been' format Linux, MacOS, OpenBSD and ChromeOS logos on top of the Earth The first astronaut says 'Wait, it's all Unix?' A Windows logo, on top of the second astronaut. The second astronaut says 'Always has been' and points a gun to the first astronaut.
Windows was this close to be Unix. Windows was POSIX.1-compliant, and Windows Service for UNIX was also a thing.
That is Windows NT personalities. It was originally able to run OS/2 stuff too. Doesn't really make NT a UNIX. Note: They used this stuff for WSLv1, but it was slow and had same issue as WINE. Swapping underlying implementation brings out bugs of the software above.
I'm more of a "if it swims like a duck, quacks like a duck, then it's a duck" kind of guy.
That is a low bar for duckdom.
I never thought I'd find a duck with a whip attractive, but here we are...