My 99 , the switch is to cut power to the LP leak detector only. The detector is not wired through the battery cut off , so would stay on continually in long term storage.
An LP shut off solenoid is mostly used in coaches where the service valve on the tank is not easily accessible.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.