I offer nothing about the arguments re powered aircraft, but the original poster was completely wrong to say “And a glider does not have power to adjust the glidepath (sure it has speed brake but I am sure most glider pilots do not pedal their way down final with that control).”
I don’t know why the word “pedal” was used, but for the record, glider airbrakes or spoilers are hand controls.
All gliding operations in the UK teach that you do indeed use the brakes continuously if necessary, to maintain glide path towards a reference point, in particular below 500 feet. It is often the case that they have to be reduced when descending through a wind gradient.
The elevator is used to maintain airspeed. With some gliders, a small change in elevator is required to maintain airspeed when the brakes are opened significantly more, but the essence is always elevator for airspeed, brakes for rate of descent.
Trying to point to where you want to go in a glider would lead to potential disaster in attempting a field landing with limited room for flare and ground run.
If you want to teach something else for power, or (worse, IMHO, teach different things at different stages of learning), feel free, and be aware that converting glider pilots to power you will need to explain why it is different, but please don’t propagate misleading advice to anyone learning gliding. There is standardised training of gliding instructors to a standardised syllabus in the UK, and we do what I have said, and not what Boof says..
Chris N.