Sorry to be pedantic, but the flow is Transformer->Distribution Center->Supercharger Cabinets->Charging Stations (Stalls, Pedestals). There is one Distribution Center feeding multiple Supercharger Cabinets, each feeding two Charging Stations. See my earlier post, #124 for reference.
As to Cabinet #5, it's clearly for future growth. If you look at pics in JST's post #123, it is pretty obvious there is space for Cabinet#5. It is common practice at Supercharger Sites to install conduit for one or two spare/future growth cabinets.
I hope for 135 kW cabinets in all the new installs. It's clearly labeled on the cabinet; this should be easy to see through the bars. BTW, with a typical 90% efficiency, 135 kW out, needs 150 kW in per cabinet. If all 4 cabinets are at full power, that is 600 kW, technically more than a 500 kVA transformer can handle. However this is a peak, low-probability case, and utilities commonly overload transformers for short periods of time. If someone gets a chance, see what the transformer rating is. It should be stenciled on the transformer somewhere.