Thanks for all your efforts on documenting this one but I would never strike this scenario because I do not quiesce.
When I require absolutely bullet-proof backups for mission critical vms, which I have had for several years thanks to ghetto, I leave nothing to chance and shut the vm down before backup.
If you are unable to do so then you should pay a larger sum of money for your backup solution.
I have always viewed quiescing as a smoke and mirrors black art and studiously avoided it - hence no problems!