In my case the Wallbox goes to the Waiting state once the car says charge is complete. (As it's an SE SR then I always charge to 100%). Waiting means that it is waiting for the car to request a charge - as it is at 100% already then it won't, but the car also won't let preheat happen as it is plugged in not charging ... Catch 22.
I totally see your point !.
I am looking at it this way ( in my case ) at least.
The rather large battery on the ZS EV LR has more enough capacity ( when charged to 80% ) to suit my usage pattern just fine.
It has been charged overnight using our current cheap rate deal of 4.5p/kwh rate for five hours.
The preheat facility is brilliant and intend to use it regardless of where the power is coming from to supply it, to be honest !.
If I do pull the juice from the wall box in the morning, then it is costing me 40p/kwh so why bother.
I used the preheat facility three times this morning, conducting back and too school runs etc.
It instantly reduces the range by about 10 miles from the GOM of course.
Am I bothered, no not at all !.
I can afford to lose that amount of range in exchange for the benefits of getting into a frost free toasty car !.
The seats in the Trophy can be cold in the winter time, so preheating the cabin really help with this problem.
It's a shame they disabled the heated seat function from the App or I would used that as well.