Very curious to find out what capacity transformer is provided for this site, it being a V3 charger and all. 20 x 250kW is 5MW, but based on existing chargers, I wouldn't be surprised if the transformer is smaller capacity than that.
From some existing superchargers, it's clear that Tesla oversubscribes a bit, knowing that it's highly unlikely that every charging stall will be going at 100% capacity at the same time.
Also, the presence of powerpacks can offset some of the peak load.
Finally, I highly suspect they have the ability to configure the charging station to enforce an overall maximum power limit to stay within the transformer's capacity.