Most hypervisors don't try to hide themselves from the VM. Many provide interfaces from the guest OS in the VM to the hypervisor for things like para-virtualizing device drivers for performance, ballooning (reclaiming unused RAM), or many other features.
The point of the project in this case is to detect the hypervisor from within a child container (which has a virtualized /proc and /sys).
Hosting providers do this with their Virtuozzo products so they can take advantage of memory deduplication. Such information can be helpful in diagnosing performance bottlenecks (think paravirtual steal-time).
