After talking with a few Audio friends, we concur that probably the reason for the 20A IEC on the back of some component is to ensure that whatever power cord is plugged into it can handle 20 amps and consists of 10-12ga wire.
That is; all premade 20 amp power cords that I know of do come with substantial internal wiring.
Of course anyone can put a 20A connector on any cable regardless if it has 10-12 ga wire inside. Then, there are the 20/15A adapters we use, who knows what type of gauge is used with them.
ozzy