I guess that it depends on the point of view of the user. For those playing "traditional" music (concert band, Broadway show books and the like), there's little call for such technique. So, as long as you stay in this comfort zone, you can pretty well ignore anything above a high F#.
I've had zero skoolin' on the saxomaphone, and until just the last few years had no need for stuff above the fingering chart. However, as I grew out of playing shows and into playing pop stuff, I was suddenly exposed to the occasional altissimo A natural, a note that I cannot get to consistently pop on my Yamaha YBS 62.
I'm not about to start in on a regime of practice so as to nail these few and far between tones with the same degree of musicality that prevails on the rest of the horn. I either drop them an octave, or do a controlled "squeal" (the notes are written as "squeals" anyway).
Some day, after I've mastered the basics on the flute, I might take a shot at the altissimo methods. Some day...