Amazing how people still fall for the "baremetal" marketing pitch. There is no such thing, or rather if there was, it would have been implemented in firmware and not software.
You need to understand that any x86 machine needs an OS to operate, you need drivers to interact with the hardware and process control, schedulers and so on, otherwise, you cannot do anything. The "baremetal" part of any OS are the drivers, since this is the part that interacts directly with the hardware. Intel VT and AMD SVM are also hardware, and a hypervisor is pretty much a driver for this hardware. ESXi is an OS, trimmed down and designated for specific kinds of load, but an OS nonetheless. KVM is that very driver for VT, and since Linux (the kernel) already has the rest of the hardware support and schedulers in place, to become a proper "baremetal" hypervisor, all it needed was the KVM module.
Now you can argue which approach - reusing the Linux kernel, which has been tested and proven over the years, or rewriting it as a new OS is better, but essentially, there is no such thing as a baremetal hypervisor for x86. Leave marketing alone and pick the hypervisor that suits your needs.