Same when someone claims to have written an OS in 1000 lines and all it does is get you to real mode with VGA graphics and an interactive (but useless) prompt.
(Note that you can benefit from virtualization technology in specialized scenarios outside common hypervisors, but that's not really what's being demoed here.)
Other small OS's are actually OS's and can be impressive efforts. Sometimes they bring new concepts or paradigms, but that itself is rarely more than a curiosity without impact. Still fun though, at the very least for the authors.
It would be nice to see a demo!
I'd say it's a good place to start !
> We'll implement basic context switching, paging, user mode, a command-line shell, a disk device driver, and file read/write operations in C.