Warning not showing up for isolating Passthrough devices

If you go to 'System' -> 'Advanced' and go to configure the Isolated PCI devices at the bottom, the form is supposed to show warnings in certain cases. For example, if I have just one GPU/PCI device available and I try to isolate that, the form should not be submittable and I should see a waring. Something to the effect

"With this selection, no device is left for the host to consume."

The warnings are already present in code. They are just not showing up at the right place. It might have something to do with the newer validation errors logic or might not. Needs to be checked.