Out of interest, I tried flashing the printer with the switch in the OFF (run) position and it failed to detect the COM port the printer is on. With the switch in the ON (flash) position, the COM port appears in device manager. I think perhaps my explanation of this mod wasn't clearly articulated.
The switch replaces the jumper on the board that you need to switch over when flashing via USB. With the USB plugged into the PC and the switch in the ON position, the LCD turns on and I can flash the board. With it turned to the OFF position, I power up the printer and melt plastic.
I did the mod because I got tired of having to open up the control box and remove the power supply simply to switch the jumper over. This makes life so much simpler, especially when you want to turn things on/off one at a time.