I've been studying 'The Jazz Theory Book' by Mark Levine, which presents this stuff in a systematic, practical, and clear way. However, the one thing about many of the figures mystifies me. For instance, on pg 15, fig 2-1. This is supposed to be my ears first exposure to ii-7 V7 I, but what I get is a ii-7 plus the 9th. I understand that in this case, the 9th is part of the melody, but to my relatively untrained ears, it obscures the harmonic motion I am supposed to be internalizing. Likewise with the first chord in fig 2-3, 3-37, and others? Are these errors? Poor choices for examples? Or do jazz musicians think of all chords as 7th chords and don't bother to notate what additional color notes like 9ths and 11ths are added?