Not necessarily. XENIX (SCO Unix) was the best-selling, and extremely well-thought-of, Unix that Microsoft had as its flagship OS from the late 70’s into the mid 80’s.
At that time, they considered Unix their “real multi-user” operating system, whereas MS-DOS was viewed largely as a “single-user toy” within MS. Things changed after the Apple Macintosh, when MS realized they needed to come out with Windows, and they sold XENIX to SCO. They then concentrated on OS/2 and later NT, as their “serious” operating systems.
“They then concentrated on OS/2”
The good old pre-internet days. 1992 I was working for Ross Perot. A co-worker was holding his off the shelf retail box that read OS/2/Warp on the outside. He proceeded to unload his critique of me. Fun times! I knew jack about computers back then. These days I put/upgrade nvme into laptops and sell them.