So it turns out my old case had the two switches in line. I did some research and would appear that these are both wires in parallel. If one dies then the other serves as a backup. Ashcrofts have blanked one of the holes. I'll probably just run with the single new switch that they installed. I imagine the built in redundancy is for the NAS market where lights are very important in making people aware that they are driving around on bitumen with diff lock engaged. The top switch that I originally enquired about is a neutral switch that does not appear to be required.

