As a former student of the Maggio system (and acquainted with the program for some 42 years approximately) I think that just maybe, perhaps slightly I'm in a position to make comment as to its validity. What ya think just MAYBE???
ALL syllable systems ie Louis Maggio, Claude Gordon etc, are flawed. Now this doesn't mean that you can't learn anything from them. But at least as they explain themselves they are all FLAWED. Each syllable system, as described would require a violation of physical law which simply can not happen. No more than one can violate the law of gravity, the restriction of air within the mouth cavity can not by itself influence the air pressure available at the embouchure release point inside the mouthpiece.
Can not possibly happen. Is not like a "maybe some of us work this way" Au contraire NO ONE can violate the laws of physics. I have little patience for those who attempt to defend or promote the false "faster air" argument and simply won't respond to them. Not any more..
IF (and the key word here is "If") there is a physical advantage to a forward tongue movement (upon range/tonal production on a brass instrument) within the mouth it could only be associated with the tongue's impact/effect upon the embouchure DIRECTLY through touching or not touching this.
However the antiquated Gordon and Maggio lessons do not describe this reality. Again this doesn't necessarily mean that you can't learn anything from the pedal tones or exercises. But if we are responsible and interested in what really makes the thing work? well we ought to look for the real causes of helpful tonal production.
And if a forward tongue movement is occasionally helpful? then this matter ought to be researched, investigated and explained.
Arturo Sandoval and Jon Faddis are extremely gifted trumpet players. Granted they worked very hard at their art. That said however almost ANY SYSTEM would have worked for each. they're natural players. With most natural phenoms about the only thing that the average masses can derive from them is inspiration.
Some, like Maynard Ferguson and Doc Severinsen knew and acknowledged this. They knew they were natural players and it is to their credit that they admitted it. Most phenoms however however don't. I do not know if Sandoval and Faddis are cognizant of these facts and so won't comment. Although we ought to at least wise to the fact that Sandoval is teaching the so-called "faster air" method which, at least as explained can easily be refuted. This doesn't make Arturo a bad person it just means that what he explains in his heart is not really what happens when the tone comes out his horn.