Yes, the initial goal was for crosvm to be a thin hypervisor, just running the kernel directly, but it's expanded in capabilities (and complexity) over the years.

I'm working to expand on ChromeOS's current Crostini system to let it run more generic VMs, so part of that means being able to boot from a normal UEFI disk image and locking that down from the inside using secure boot so we can run things other than the official Crostini offering.