Obligatory:
Vin Diesel Rips Paul Walker (The Fast And The Furious) - YouTube 
In any case, it is factually true that even on a modern transmission, using a double-clutch technique (in addition to normal rev-matching) will make the engagement smoother. When combined with heel-toe on a downshift, the extra release-push cycle on the clutch pedal mid-shift (while the stick is transitioning through N) basically serves to "rev match" the front side of the transmission to the engine revs you're blipping up to for the next gear. I only ever tried this playing around on the street a bit, I have no idea if it's practical.
Either way, the whole double-clutching issue is orthogonal to the basic questions about skipping gears on downshift (although as you skip more gearing, double-clutch might become more worth it).