So this is basically saying that we can no longer depend on the OS to protect us against privilege escalation attacks. The bad guys will have to concentrate on breaking out of VMs or, at least in this case, attacking through the access that the Edge VM has to system resources.
No modern OS is immune to privilege escalation attacks. Even a formally verified OS would probably still be susceptible to them due to unexpected interactions. Never mind hardware based attacks such as race conditions and rowhammer. If someone is dedicated enough, and has enough resources, sooner or later they'd find a chink in the armor.
Instead you try to do the best you can, and then you layer on defense in depth on top of that. If someone is going to break in, then you can at least slow them down and force them to fight another kind of complexity.