[flounder3]

> The only function of the box is to switch the power on and off

That is false. These are much more sophisticated than a mere relay. Sure, there is basic logic between vehicles and EVSEs which is basically a smart relay: https://en.wikipedia.org/wiki/SAE_J1772#Signaling

...but the electronics you mentioned are for onboard controls (energy monitoring, Time of Use enforcement, load balancing between multiple units, etc). Some EVSEs are very simple, but many -- including the one in the article -- also handle upstream communication like OCPP: https://en.wikipedia.org/wiki/Open_Charge_Point_Protocol https://www.chargepoint.com/files/OCPP-Fact-Sheet.pdf

Here is an example of integrations for the model in the article: https://zaptec.com/downloads/ZapChargerPro_Integration.pdf

There are also implementations of power line communication over the Control Pilot pin in J1772, which most people notice when charging via CCS at a DC Fast Charger, but that is not limited to L3 charging. Note that QCA7005 chip in the article: https://www.qualcomm.com/products/application/wireless-netwo...

See also: Plug and Charge https://en.wikipedia.org/wiki/ISO_15118