How does the Learjet cabin pressurisation system work?
If the pilots know the system, it isn't confusing at all.  It simply states that a solenoid valve closes causing the cabin pressurization system to go into manual mode and the pressurization controller cannot control the cabin pressure.

It is a feature of Learjets to prevent cabin pressurization issues in case the controller is faulty.

Since you reference the Payne Stewart accident you should also know there were other issues at play that did not cause the pressurization controller to fail.  It was one of the early Learjet 35's without an emergency pressurization system.