As the tow device is physically connected to the glider I assume that is considered its own power? But I have no interest in checking.
Not the fire again!!!
What part do you not understand of when we can ABSOLUTLY say and legally prove when a pilot is "In Command" and has those responsibilities.
But we can not prove that they are responsible before that point in time.
As before common sense, right thing and assumptions are not regulations.
You can not prove you have responsibility - I can prove when you will/would have it not only that I have.