CFI - That is an old teaching, since discredited I fear.
Airprox - You are dead right. When starting on circuits with new student I prefer to use throttle off glides right from the start. ie Turn level base, and when sure you can glide in, close the throttle completely and use flap as needed (Cessna 150's et al) Same as Tiger Moth technique 50 years ago. Speeds are the same anyway. Naturally you have to control IAS with elevator in a glide. Teaches good judgement nice and early. It works, too. For powered approaches use fixed aiming point and control IAS with throttle. Actually it is a combination.
Same when using VASIS or ILS. Works wonders and I seem to get students to go solo between 6 and 8 hours using the above techniques. Forgive me if I now hurriedly exit stage left before the knives arrive!