But the IMC exam treats the AIP recommendation as the legal limit, and bases the correct answers on that.
No, it bases the answers on the recomended minima which is what they have been trained to fly to. I doubt that you will find any question asking for the legal minima and it is not unreasonable to expect a candidate to know the recomended minima for the holder of such a rating. They will be required to demonstrate it on the flight test.