This qemu support comes after Amazon added support to the kernel to emulate Xen when combined with their custom vmm. A key component of that is the hypervisor lying when it's asked by a guest to describe itself.
There's a good chance that 'xen' box is actually KVM and Amazon's proprietary vmm.
You either die a hero or live long enough to see yourself become the villain (ie. last vestiges languishing as a compat shim that even the developers who support you wish they could finally deprecate and remove).
