Firstly the CFS aspect. I started my career as a baby pilot with a RAF Flying Scholarship, standardised by CFS, and this was certainly not the approved light aircraft technique back then (1989).
Student pilots should be taught to fly the aircraft! Using the 'standard' techniques, if the student has an engine failure for real, then it shouldn't be too taxing for them to subsequently trim the aircraft for the glide. After all, isn't this what the rest of us practice on PFLs/EFATOs?
From an instructor's point of view, getting the average student to close the throttle fully on base leg and then having them select 20 flap and trim for the glide would put the aeroplane well below the ideal glide slope. Huge out-of-trim forces on the go-around, anyone?
Fairly recent echoes from my BCPL course: "Keep the aeroplane in trim at all times.". I doubt that CFS is teaching otherwise...