[AnthonyMouse]

> And if you can get around the digital signage, you don't need the compromised OS.

Not necessarily. Someone could get their hands on the signing keys or find a vulnerability in the signature verification without having the knowledge or resources to create something worth signing. Or figure out a way to bypass the check by changing something that isn't covered by the signature, or use something like rowhammer or hardware hacking to flip the bit from saying the check failed to saying the check passed, etc.