They did actually merge the products around OpenServer 6/UnixWare 7. No, the names don't make a bit of sense.
While SCO licensed Xenix from Microsoft and kept the port going through 386 support, SCO Unix/ODT/OpenServer/UnixWare all descend from a separately licensed SCO System V release 3 port, not Xenix.
Disclaimer: I worked for the company that wrote the (in)famous C2 security subsystem for SCO.
It's been so long since I've touched OpenServer (say, ~20 years) that I can't remember if the technical bits of the page are actually OpenServer or UnixWare (I'd say OpenServer). OpenServer had Xenix as a predecessor and, though I didn't work with UnixWare at all, what little I did play with it made clear there were some substantial differences.
All of this is all but historical trivia now, but I'm sure there are at least some OpenServer installs running out there... somewhere....