EV9 charging speed on tesla superchargers V3

I have seen real life reports of EV9 charging at 84 kwh on tesla supercharger V3. Why is it so low? What is the bottleneck?

Supercharger: 250 kwh, 480 V, 520 A

EV9 max speed: 210kwh, 800V, 262 A (210,000 / 800V = 262)

If we assume EV9 is limited by the current (262) amps, we should reach 125 kwh. Unless the DC-to-DC conversion to increase voltage to 800V is really innefficient!

I also read that official specs from EV9 says the battery is 552V. Does that mean that a CCS the charger is pushing 210kw/552V = 380 A ? If this is the case then, should we be able to charge up to 182kwh minus some small dc-to-dc conversion innefficiencies? This is far from 84kwh.

Can someone help me out make sense of these numbers ?