Today’s EV charging network overwhelmingly operates at 400 volts, while an increasing number of EVs have 800-volt electronics that can exploit the faster charging possible at this higher voltage.
The Audi e-tron EVs have two ports, but they are on opposite sides of the car and are there for ease of connecting to the nearest one. But connecting to one of these automatically disables the one on the other side of the car, so the e-tron cannot exploit two charging stations at once.
The GM system can not only use two low-voltage charging stations at once, it can also use one high-voltage charger and one low-voltage charger at the same time. In this case, the high-voltage charger does all of the work charging the batteries, while the low-voltage station can power the vehicle’s accessory loads.