No doubt that’s true, just questioning the way it’s being presented as an either-or situation. While transcribing, playing along with looped phrases of Paul Desmond, say, trying to match the minutiae of his inflections, vibrato, phrasing, voicing, recording myself, am I not “working on tone”? Is it possible I would accomplish a satisfactory version of the Desmond solo yet because I didn’t specifically trade in some of that time for working on only one note at a time, my tone will surely be pinched? Aren’t I “working on breath stamina” whether holding one note for 12 beats or playing a 12-beat long (mostly) legato phrase on one breath?I'd also point out that if you know 1000 tunes but play with a pinched dull tone and bad intonation, no one will want to listen to you; but you can play the simplest stuff with a big rich compelling expressive tone and everyone will want to listen to you.
I’m a longtime voice teacher and there are certainly many analogous exercises only working on tone or breath-control with voice. But you know who else also typically has great tone and breath-control? Plenty of singers who just sing a lot of repertoire and work to realize its full expression. You can build huge calves doing reps on the machine at the gym but also bike messengers have them without stepping foot in the gym.
To clarify, I have nothing against long tones, I play them sometimes and actually enjoy them. I started sax a year and half ago doing them for like 30 minutes every day and after several months I just couldn’t shake the nagging feeling that I could be better applying that time to something else. It’s just based on my experience coming from other music instruction that anytime you’re doing something that’s “not playing music” and doing it repetitively every day etc, to build muscles, whatever— let’s just say I really question that. “Musical Calisthenics”, “Bootcamp” this kind of attitude. “No Pain No Gain”.
On piano we have the Hanon and Czerny exercises that so many pianists sacrifice untold hours of their time to playing, to gain the skill to move fingers faster with what I’d argue is close to zilch artistic benefit. Like: just play Bach and you’ll get up to speed eventually but with heavenly melody inspiring you every minute along the way.