I seem to recall the WCC people say that the heels should stay down as you pull the weight up, but as you try to pull yourself under the bar, the explosive force of the hip and knee flexors may pull the heels up off the floor. So in essence, the heels are used to drive as you are coming up, but the heels tend to lift as you pull yourself under. That is significantly different than the idea of triple extension.
If you watch Dan John's avatar of Pyras Dimas, he seems to drive off his heels and then the heels seem to lift as he is pulling under the bar. It's extremely fast, but I think that is what he is doing.
Another difference, is that the USA Weightlifting want a perfectly vertical pull whereas, the WCC advocate a pull and backwards motion where your head and shoulders move back and you look at the ceiling briefly at the maximum extension. Again, look at the Dimas avatar and notice how far back his head & shoulders go at maximum extension.
How do you guys feel about that?