Alex, what we are talking about are not necessarily artistic choices; and, in the case of Dizzy, I don’t believe they were. Moreover, we may be misinterpreting, what the author of that quote is saying. Some jazz players cultivate the ability to sound loose or with a "casual" attitude in their tone for artistic expression. Miles was that kind of player; he could sound beautifully in control with excellent intonation and relaxed tone and if he wanted to other times sound the way a beginning trumpet student might sound. He was in control. Other players simply didn’t learn to play their instrument in a way that allows the tone to be fully developed and with good intonation. This is rudimentary in the physical act of playing a wind instrument. Dizzy was a completely self-taught player and he put emphasis on fast playing and high playing. While this fact, unto itself, may sound impressive, it is rare the self taught wind player that doesn’t develop some terrible playing habits. There are ways to accomplish the speed and range and still not develop the other traits in one’s playing. In fact, by starting with the "fast and high" pproach it makes it almost impossible to accomplish them. First thing any good teacher tells a student: "Play it very slowly". Moreover, his ability to improvise the way he did has nothing to do with the issue of finesse and control. In fact, it is a cliche among players that, generally, the ones who play a million notes are the ones likely to have issues with finesse and control. I have no idea whether Dizzy wanted to be able to play with the finesse and control of someone like Miles. You seem to be suggesting that he could at any moment, if he wanted to. No way! As with any other player on any instrument, if he really wanted to, sure! But it was going to require a complete rethinking of his embouchure, the way that he blows and other considerations. Reversing old playing habits could take a couple of years.
All of this may sound very calculated and in conflict with the creative spirit of jazz playing, but it is a reality that every player experiences whether studying an instrument formally or not. Many great jazz players, even if they did not attend Juilliard like Miles did for a while, started with teachers that, at least, pointed the way. There is a tendency to think that jazz players simply stick the instrument in their mouths or hands and magic happens. It’s much more than that.
All of this may sound very calculated and in conflict with the creative spirit of jazz playing, but it is a reality that every player experiences whether studying an instrument formally or not. Many great jazz players, even if they did not attend Juilliard like Miles did for a while, started with teachers that, at least, pointed the way. There is a tendency to think that jazz players simply stick the instrument in their mouths or hands and magic happens. It’s much more than that.