cheating as in they have much less work to do to implement unix-like linux on the hood because it was already there, and Microsoft actually has to build a port.
Would doubtlessly be fun.
Before that, MacOS had (AFAIK - never seen it myself) the MPW environment that had a Unix-like shell.
And A/UX.
Practically an entire BSD kernel is run as a single "server" in Mach. In Apple's open source release, a majority of the XNU kernel code lies in the "bsd" subdirectory -- Apple's heavily patched 4.3BSD / 4.4BSD / FreeBSD hybrid.
Originally the idea was that having most of a BSD kernel running inside Mach would make it easy for researchers to run tools on their research kernel.
One suspects NeXT had a simpler motive: They just wanted to avoid paying money to AT&T. I'm not sure they had any particular interest in Mach itself. (Although obviously Mach's strange multi-architecture binary format paid off for them big time, some years later!)