True, and as another commenter hinted at, you're free to do your own hobby project however you please, there's not a wrong way to do so if you find it fulfilling.
But at the same time, it does make me sad that most hobby OSes end up seeking POSIX compatibility, because that means being destined to essentially either be another unix-variant or develop a unix-variant inside some subsystem of your OS.
Yes, being unix-like means you gain access to a trove of software and libraries that makes porting applications much easier, but it also limits the potential be truly different and experiment, as your end result will look like "yet another unix" with misc. improvements.
Since I think the enjoyment of building something like this comes from the satisfaction of building an OS from the ground up, I don't think it matters, but it would be cool to see more hobby OSes try more exotic ideas and runtimes.
So, a preliminary problem for many OS-from-scratch projects intending to create "New Different Great OS" will be to have a language implementation which does not expect posix.
It depends on the goal. If you want to compile pre-existing software for it, or if you want to really "start anew".
