Its my understanding that the inverter is still on the truck, and converts the high voltage DC to 220v AC that the normal level 2 charger on the wall takes. The marketing being the truck can backfeed your house if the grid is down. However it would seem that requires the charging station on the wall to be grid sense aware and have other ATS aware features. You wouldn't want to be bleeding back to the grid when it was down. (unless the grid was up, and you were using it to grid balance)
But the point is, have seen no docs that suggest that high voltage DC is designed to come out of the charging port with a home lvl2 charger. (what your saying would mean there is a 300v dc inverter on the wall and again I'd be interested to see the links to the specifications of that hardware.)