I teach on 172SPs and use both techniques. I start with the 'powered' approach because it helps to demonstrate that throttle isn't a 'speed controller'; it is an aircraft control and therefore has a number of interlinked effects.
CowsgettingBigger.
Here I am going to disagree with you
Both throttle and column are energy controllers.
One taps into energy from the engine the other taps into potential energy in the airframe.
A glider has no engine as such so its throttle (if you like) is the stick and in still air is the only link to tapping into the potential energy of the airframe.
Add the engine and you now have another source of energy available.
Both are sources of energy so ignore one at your peril
We are back to the old arguement of pitch for speed or power for speed neither which is totally correct as it should be pitch for energy power for energy.
pace