I've heard it talked about as "in" and "out" tones. The notes of the basic triad are the furthest in, then the remaining notes of the scale- then finally the outside chromatic/passing tones.
One question I do have of the chordal approach is that any given note will appear in 3 different triads - so the issue of which chord to choose starts to get challenging-
ie for the key of C major and a melody line say of "F A C E" you could harmonise with - for example Fmaj7 all the way through or change from Fmaj to Cmaj or Fmaj to Em etc- so it is all very well playing "the chord tones" - but which chords?
This becomes especially relevant when you try to figure a tune out by ear-- the melody and solo are easy but the chords require more thought.