From "A Love Supreme" to "Kenny G" in less than 40 years - we obviously can't look to jazz for evidence of evolution therory.
Seriously though - lottsa smooth jazz seems to employ more advanaced harmonic movement than simple 2-5's and modal grooves - but then again - there is TONS of that stuff so it probably IS the majority of SJ harmony.
I'm always dismayed by how much musicianship you can hear in smooth jazz underneath the layers and layers of babyface style production and 4 on the floor drumming.
As for learngin the stuff - I think if you put on your local smooth jazz radio station - and play along for a few hours on a sat afternoon you'll be able to figure out the basics of "smooth jazz" harmony and notice some patterns - aside from the same 30 songs being repeated over and over - he he! Guidlines for smotoh jazz bass - slap a lot and lock with the kick - and any other "rock/R&B" type stuff that some have said dumbed down jazz.
But not me - I would never say that.
