Depends on where you installed the disconnect switch in the line.
You may have other 12VDC cables hooked up to your battery terminals that may not be in the line you have the disconnect switch installed.
If you only have one cable connected to the NEGATIVE SIDE Battery Terminal going to FRAME GROUND than that would be a good spot to install the disconnect switch. Once it is OFF then the battery will not be able to power up anything... Has no path to ground to complete the circuit.
If you have several wires connected to both battery terminals then you will need to install a BLUE SEA LUG TYPE TERMINAL STRIP so that you can make all of the same terminal connections using ONE CABLE. Then your disconnect switch will OPEN UP all of the cables when it is OFF...
The DISCONNECT SWITCH should be working the same as if you physically removed the BATTERY CABLE from the battery terminal.
Guess this all makes sense...
Roy Ken