MFU Coupler Switch: Required?

[Rick.K]

I'm building a Knight Hauler. I have the MFU01 and the motorized leg supports kit. The 5th wheel for the motorized support leg kit does not make any provision I can find for installing the coupler switch (J12) that came with the MFU01.

I seem to recall having read somewhere that the trucks electric motor output is reduced until a trailer is hooked up. True or false?

Is this the reason for the coupler switch, and if so why doesn't the motorized support leg 5th wheel incorporate the switch?