The loadMatch switch turns on and off a feature in the computer. ON, the computer monitors the engine speed; should it drop off to a unsafe/inefficient level, it adjusts the transmission rate to a level that unloads the engine.
the only reason that I can see to ever turn it off is for diagnostics. It is never a good idea to stall the engine, leaving LoadMatch off is like leaving 4wd off to save the front tires, only to wear out the rears...