It is closer to FreeBSD for many things, closer to OpenBSD for others. I get the impression that the author does not use it which is why it is not there.
It's used by plenty of embedded vendors. It just isn't generally deployed as a general purpose OS or server by most people. Not really the goal of the project either - their goal is generally "run on any piece of hardware ever created".
It makes a perfectly decent server OS and people do use it as exactly that. The portability goal is more about writing reasonable portable code, not running on everything, indeed it runs on fewer devices than Linux, but it is easy to port if you wish to.