That's only half the equation. The other half is the complexity of the design along with its assurance activities. It's why the security and separation kernels with user-mode VMM's either had no or few flaws in pentesting. Whereas, VMware's techniques take a pile of complexity, are built with less assurance (see parent comment), and process malicious inputs in privileged modes.

Definitely designed and assured to be shattered. I'd like to see what results they get on mCertiKOS or Muen.