The issue is that the longer the cable the less the voltage at the end due to the accumulating resistance. You can get away with it for non-PD applications quite cheaply, Anker calls that VoltageBoost. PD cannot use VoltageBoost.
For a given Wattage, you have to make 10ft cable 41% thicker than 6ft cable to still pass PD.
So this is quite intelligent of someone in Anker, who is avoiding a “doesn’t work” warranty claim issue from PEBKAC. Anker sells Powerstrip and desktop chargers with C7 cables instead. C7 can go to 30ft long.