When are people taught about a set point?
ALL beginning students ARE taught the concept. As first year students the range falls between low g and 4th space e. They are taught to set for a second line g. This prevents the need for lots of shifting, curling……
The problem comes in year 2 when the range increases the center of range starts moving up. The set point should as well.
Poorly trained teachers are the reason this and a hundred other things are not taught.
If you use a pivot and open (lower) your jaw as you descend. The g on the staff setting should be easy to add to your full time playing.
The concept is about setting closer to the needed top note than the needed bottom notes. In some groups setting on a middle c might be enough. In another ie playing Si Si MF (up to g over double c) setting on high c might be better. There is an old Big Band chart Harlem Nocture where it is almost all below low c. The set point on this is of course lower (second line g).
If you can set for about an octave under the top note played then you get the benefits. This is a flexible IDEA it moves according to the range needed in a piece.