I thought the blue flashing light signified State A. To go to State B requires the controller to be able to see the car (CP at 9v), which would require the cable connected at both ends. There shouldn’t be a difference between tethered and untethered in that respect.I have a 2017 installed tethered Rolec charger - probably the same as yours but because it's tethered the cable can't be disconnected so it doesn't go into that flashing blue light mode.
I modified the firmware in my Rolec a while ago so I could control the current so I don’t remember exactly the sequence.When switched on, my charger flashes blue. When I plug in my untethered cable to the charger it turns solid blue. When I then connect the car, it turns solid green.