can they explain why recovery from the stall enforces reduction of angle of attack rather than increasing airspeed?
Quite simply you need to reduce the angle of attack in order to allow the air to flow over the wings. Full power is applied to merely reduce the amount of height lost.
Its also important to get the student to reduce the angle of attack of the wings before applying the power as done the other way round can cause the problem to get worse. In certain circumstances I get the student to recover by merely reducing the angle of attack of the wings and then later on introduce the power.