IMHO, using power to control rate of descent and nose position to control speed is the appropriate way of teaching basic approaches in a light single engined aircraft in visual conditions. This is because any angle of approach may be necessary due to the circumstances of the approach be they flap failure, engine failure e.t.c, e.t.c. The approach technique using power to control speed and nose attitude to control rate of descent is another technique in the armoury of an instructor to enable a student to gain the basic principles. "The vital thing is to appreciate the visual picture," as Firefly Bob's Dad used to say. The other technique is however the appropriate way of flying approaches on instruments as I have said previously. From my own experience, it was a number of years after I gained my PPL and instructor rating that I had the opportunity to try and fly a full ILS approach. I was heavily grounded in the nose for speed, power for rate of descent technique then which I taught exclusively. When I had a go" at using such things as ADF's and a full ILS system I found following the glideslope accurately very difficult: "And commercial pilots are able to follow it to 200' AGL - coo they must be clever!" It was only when I was taught the technique mentioned above on my own IR course that I found out how to do it properly.
I used to say that "flying a glideslope is just like flying straight and level - on a bit of a slope" and when you are used to flying the usual 3 degree glideslope, the visual picture of flying a 5.5 degree one at London City is totally wrong - it works though - all you have to do is to follow your instruments!
P.P.