It's not really the thickness of the cable, is it? The constrained part, that has to stay the same regardless of what cable you buy, is the thickness of the pins on the connector. Where, presumably, any resistive heat from that connection is dumped into the body of the device being charged (just like resistive heat from operating a 1600W space heater with a big, thick extension cable gets dumped into your the electrical box behind the socket it's plugged into.)