That's not how it works. DCFC actually communicates using powerline networking (specifically ISO 15118) using the big DC power pins.The reason I figured the EVSE should be able to display current SOC is that DCFCs do...that tells me the SOC data is in the "data" pin of the J1772 connection...just a matter of decoding and displaying...no?
This means that when you plug in a regular, non-DCFC J1772 connector, there is none of the communication that occurs with a DCFC station. All there really is is the pilot signal, which is an almost one-way communication from EVSE to car that simply says “you can draw X amps”. (There is also a “plugged in”, “turn on”, and “stop” signal back from the car.) Read more about it here.