C wire adapter schematic

I received the following schematic from Wyze when inquiring about two transformers and separate wiring from air handler and heating.

I am a bit confused here. It looks like they are using the c wire adapter in reverse and it is not plugged into C at all at the thermostat. Anyone have any experience here?

The C wire adapter is used to send the power down the G wire if you don’t have a C wire or extra wire to use as a C wire to go to the thermostat. The adapter connects to your control board and wires going to the thermostat.
I’ve been using the adapter and it works perfectly.

@Brlepage, I only have 3 wires from air handler. Check out the schematic, it is not the orthodox install.