This is useful if you run the G-Force in a parallell effect loop, i.e. an effect loop where a portion of the signal is branched off and sent to the effect in parallell with the rest of the dry signal, as opposed to a series effect loop, where all signal are sent through the loop.
Most guitar amps have series effect loops.
A 3-way setup can be used when you don't want the dry signal to be colored by a digital effect, but it also has disadvantages. At the same time, if there are no effects in a preset, the dry signal will not be killed. This is not a program bug, according to TC Electronic, but a deliberate design solution. This means that the Mix Level parameters will actually work as level parameters. Making Killdry Patches Unfortunately, the way the Killdry works means that your ordinary, no-killdry presets usually does not work too good with the Killdry turned on, so you must make new ones for the occasion.