Based on the article, they must have a way to prevent the Tritium chargers from all going full bore at the same time. They have 180kW grid plus 250kW battery output. So, the aggregate must stay below 430kW even though they have a total 750kW nameplate of chargers installed.
I'm aware of a couple of 2x 350 kW sites which have a grid connection of 500 kW. In reality, two Model 3s at full speed ~ 380 kW, two Ioniq 5s (when they are here) at full speed ~ 450 kW. It would only be if two Porsche Taycans were there at the same time (and they were both at low SOC and all other environmental factors were optimal) where the site power supply would be limiting factor.