Apologies accepted all around--and, a day later, as I look back at what I said, I may have put too fine a point on it-

Your Jazz teacher was probably referring to your particular situation--Jazz players work from charts and arrangements all of the time--especially in the studio, and especially when working with big band type arrangements--

As pointed out above, orchestral musicians always read--and never attempt to memorize--they are counting all the time--everything comes from the score--increasingly, mainstream "Jazz" players require strong formal music training, because much of the music they work with is through-composed, (which is to say, it has a more complex architecture than simply that of repeating the verse structure of a song) in the manner of classical music--so memorization is not practical--