While out-speeding a headwind definitely moves an airplane over more ground in a given time, and if the time is limited then it would get the vehicle farther before it hits the deck, it is definitely at the expense of time aloft and horizontal air distance over using the L/D max speed. So, we don't teach that in engine-out situations. Perhaps the reason gliders use it is they have no engine to worry about and therefore less of a need to stay airborne and to get the most air distance possible. In that case they are not using a "best glide speed" in the conventional sense of the term, they are using a "best ground distance speed", and there's a difference obviously.

[edit] I got my glider handbook out. It says the term for this kind of glide speed is "the speed to fly" (as Oldveedubs pointed out also), and it is not technically a best glide speed.