A non-technical analogy for this might be that if you drop a coin in a tube with shampoo in it, no matter how wide (low resistance) that tube, the shampoo (the Characteristic Impedance) is going to get in the way (compromise current transients). Eliminating Characteristic Impedance (Zero means No in this application) is like having only air in the tube, as close to a vacuum as possible. Whether the amp is running at less than a watt or is fully maxed out, the unrestricted transients are visceral — something the whole body understands, no words required.