The 150Kw converter option ONLY applies IF a 150KW capable fast charger operates at 400v NOT at 800v. If you do not have the converter than you can only charge at 50 KW at any 400v fast charger, even if it can operate at higher KW rates. If the fast charger is capable of 800v it will still deliver the max it can with or without that option.
So option only allows >50KW chargers that are 400 v to be used at their fastest rates. It seems most faster than 50KW chargers are 800v capable.