That's correct for all BSD's, not just OpenBSD.
BSD = kernel + userland
BSD = kernel + userland
It's much simpler than you represent.
There are only 4 real trees here:
* FreeBSD
* NetBSD
* OpenBSD
* Dragonfly BSD
In very approximate order, and I suspect that there are (wild approximation) half as many users for each step down the list.
One estimate I've seen is that there are ~7K users of openBSD, in total, worldwide.
There are a few distros of FreeBSD. None of the others have distros, AFAIK. PC-BSD was a FreeBSD distro. iXsystems acquired it, turned it into TrueOS, and then killed it 4Y ago.
Maybe it'll finally scratch the ultimate nerdy OS itch.
Probably not though.