@neauoire That is basically correct. This is why I like the approach taken by IBM when they released VM/370. The product exists at two levels. The hypervisor itself, and a single tasking, single user OS that assumes it had full control over the mainframe.
So, if I were to summarize, making a good single user OS is, is wager, more important than focusing on multitasking facilities. If you need the latter, you can always run under a hypervisor.
A bunch of technomancers in the fediverse. This arcology is for all who wash up upon it's digital shore.