The Supercharger operates at the same voltage as the battery current voltage. (or little higher to regulate the amp)
V4 is up to 1000V and +1000A
V3 up to 500V and 625A
With 4680 battery, maybe Cybertruck can charge at +1000A, so it would be 400-500kW charging.
Sorry to say that you are probably wrong and that you don't understand how it works ?
Elon confirmed that Cybertruck will use V4 Supercharging but NOT that Cybertruck have 1000V Architecture.
If Cybertruck would have 1000V Architecture it will not be able to charge att V3 Supercharger because...