NT 4 and I think Win 2K had “Unix subsystem for Windows.” They needed it for POSIX compliance.
Yeah, that's right. The Windows Services for Unix was whipped up back around 2000 so they could claim POSIX. But Microsoft never treated it seriously, it was never very useful, and they nearly deprecated it from time to time.
This time they're running scared and they know that to survive they have to attract Linux users and developers, which is a very different, and much more powerful, motivation.