It's not really a security strategy, but running an obscure proprietary operating system on a system which probably isn't connected to the internet means that you're only susceptible to highly targeted attacks by a dedicated foe.

Apparently the latest VOS release was in 2025, which means that somewhere there's a team of developers maintaining it. That's really the thing I find the most interesting, that there exists teams developing operating systems like VOS, strange DOS clones or UnixWare (perhaps less so these days). Must be a strange anonymous life.