This is exactly what my teacher has been telling me. He is a guitarist with many years experience as a faculty member at the New England Conservatory.
And Jeff I must say a big thanks - it is largely because of your writings and philosophy that I am studying with this jazz guitarist/educator. I tried for years to educate myself with books and videos. I did pretty well but when the chips were down I didn't get the gigs I really wanted. I played with some good pop bands and my rock band did well. But the really challenging jobs with the great jazz vocalists, keyboardists, guitarists, I was not qualified for. My mission now is to change that.
You are welcome. My mission was to dismiss bad musical advice and guide people to much better stuff. I am glad that I helped you.
Regarding your teacher at New England Conservatory, he is right. He knows that blanket tonality (which is what key centers are) doesn't specify the sounds you are trying to represent. Key centers are another short cut method in a long list of short cuts that many embrace today. This is why only the great teachers know the difference, the ones that I have been imploring people to seek out. NEC doesn't allow for anyone or anything that isn't of a high musical quality, which is why your teacher is teaching there.