Bear in mind that on 120 V charging losses are greater. Net to the battery is probably only 1200 Watts (half of the power @ 240 V so double the charging time).
That's a completely different discussion. But since you brought it up, the charging time on 120 is not twice that of 240. It's much less than double.
With a live voltage of ~240V, I'm seeing the PiP draw 9.6A . Which is (power factor ~1) 2.3kW . I also see this displayed on Chargepoints. I believe the voltage on the Chargepoint is lower, so amps must be higher.