If that is said during a stall, ok. Although all you need is reducing angle of attack (not incidence, probably that is what he wanted to say).
Stall occurs at an AoA. Push the stick, you unstall the wings. Of course you will loose altitude. The time to add power is usually after you lower the nose, so the effects of the propeller and others do not put you in trouble before you manage to unstall the wings.
If it is the old wrong assumption that speed is controlled by pitch, and not power, well... It is wrong except during climb or descents at fixed power, where it is totally correct. In level flight, or in an ILS, speed is controlled with power and flight path with pitch.
For instance. To maintain altitude you pull or push the stick as necessary, while maintaining speed advancing or retarding the power levers as required. Altitude increasing? push the nose a bit. Speed decreasing? add some power.
If you are studiying aircraft engineering and are interested in how pilots fly an airplane there are very nice and simple books for private pilots.