If energised, the engine idle is low (ground idle). If de-energised, engine idle is high (flight idle). The solenoid is always energised (ground idle) in the air or ground mode, except during landing approach..."
That is correct and exactly what I said in my post above. I also believe the 737 to be not much different. Selecting landing flap, will cause the FCU to schedule flight idle until touchdown with a 6sec delay before establishing ground idle RPM.
The following from my GE CF6-50 notes on the subject:
Engine control is provided by the MEC main engine control and incorporates a flight/ground solenoid which selects a higher flight idle(+14%) when airborne and flap is set at 25 degrees or more. Engines remain in flight idle for 5 secs. after touchdown, after which the solenoid in the MEC is energized and GND idle is selected.