If already discussed later in this thread, please ignore this observation:
My understanding is that any high power charging bypasses the on board charger as the on board charger is only good for 7.x kW of power.
AC Charging (up to 7KW) uses the onboard charger. It converts 120-240VAC to ~400V DC for the battery.
DC Charging (10s of KW) bypasses the onboard charger. The car gets straight ~400V DC for the battery.
Nothing bypasses the Battery Management System (BMS). It needs to run all the time to monitor and rebalance the cells.