Linux

There is no hypervisor. So, no hypervisor to update and manage.

I recently heard this great phrase:

"A VM makes an OS believe that it has the machine to itself; a container makes a process believe that it has the OS to itself."

This would be somewhere between that, where each container could believe it has the OS to itself, but with different kernels.

I imagine there's some overhead savings but I don't know what. I guess with classic hypervisor there's still calls going through the host kerbel whereas with this they'd go straight to the hardware without special passthrough features?

Saving on some overhead, because the hypervisor is skipped. Things like disk IO to physical disks can be more efficient using multikernel (with direct access to HW) than VMs (which have to virtualize at least some components of HW access).

With the proposed "Kernel Hand Over", it might be possible to send processes to another kernel entirely. This would allow booting a completely new kernel, moving your existing processes and resources over, then shutting down the old kernel, effectively updating with zero downtime.

It will definitely take some time for any enterprises to transition over (if they have a use for this), and consumers will likely not see much use in this technology.

More transparent hardware sharing, less over head by not needing to virtualize hardware.