Mandating the content of the instructor flight completely buggers up the concept of the pilot (or the instructor) choosing to make use of the flight to concentrate on any aspect of the pilot's flying which either of them consider to be the most useful to the pilot.
Whether it be circuits, landings, tail wheel flying, navigation, instrument flight, complex training, type training, aeros, whatever, it is a wasted opportunity not to use the time specifically to the maximum benefit of the individual pilot.