Glad that you verified my understanding of the battery disconnect switch with Kermit, I hesitate to challenge any of my extended family here on the PC forum - thanks for being a good sport about it.
While sitting here in the PC in Tucson, Az enjoying the warm weather I thought I would put together a very simple schematic of the disconnect switch. I did this in Excel and took a picture of the screen to upload since I can't print and scan; quality is not that great.
This is for my 2010 2551, the relay and converter are located differently in some other models, but the schematic is probably the same. The battery disconnect relay is located under the passenger side bed next to the converter/charger, the disconnect switch and light are located next to the entry door.
The disconnect relay is a latching relay that mechanically latches in the closed or open position after receiving the corresponding 12V signal from the battery disconnect switch. The disconnect switch is a two way momentary contact switch that momentarily sends the signal to the relay for both the "USE" and "STORE" positions. The "STORE" position is the disconnected or open position for the relay. You can see in the schematic that even with the relay in the disconnected open position that the light at the doorway switch will be powered if the converter is plugged into shore power and thereby providing power to the 12V circuits.
Hope I haven't got too detailed and bored everyone, but I love digging into the workings of stuff like this - my wife says it is a curse.