Absolutely correct.
I wouldn't bother removing them, loads of the bikes for sale have the frames but not the cases, so if you are selling the cases separately then I would leave the frames on. They are still available from the Chermams online.
However, unless you have the Rear mudguard (black thingummy between the tail light and the number plate holder) then it is a simple job to remove the frame, which is one piece.
If you do have the rear mudguard, then it 'might' be fitted over the rear of the rack or underneath it, can't remember off hand and I'm not at home at the moment. This only matters if the rear mudguard is fitted 'after', ie 'over' the rear of the frame. If it is 'over', then it has to be removed before the frame can be removed and the cheesy screws that hold the mudguard in place will almost never come out in one piece. I've had to drill out mine before now which melts the plastic of the mudguard. Proper screws and a couple of repair washers will allow it to be refitted properly if you do have to remove the mudguard. Good luck Ron. Brian