I have no doubt what Matt has said; I'm sure there are some that do spar and use the sine wave technique but I would be it is very few and may be school specific.
From watching videos and seeing some in person, sparring looks like sparring regardless if TKD ITF, TKD WTF, Karate, etc. There is kicking, punching, foot work, etc. If SW is that much powerful why is it not carried more over to the sparring?
[Don't read too much into this as bashing; I have seen some spectacular ITF fighters and envy their abilities. However when they fight it looks just like that; fighting, which cannot be distinguished from other fighting forms. Has their own personality and flair.]
I had an opportunity in my years of training to be invited to train with an ITF school which I did for 3 or 4 classes. I found it difficult to do the SW in the patterns however I followed along as best as possible. When it came to drills of punching and kicking, SW was not present and it was no different than the drills I did in my own school. Again if SW is that much powerful why is it not carried over to the drills?
SW definitely makes ITF stand out; it is their own. That Choi said other schools were "phoney", I think that just lowered him to the same level as other practitioners who think their system is the end all be all. I would rather train under a person, especially a system, where the teacher encouraged its students to learn other arts to see the difference for themselves and add those skills to their own to make them better. That is a true martial artists; open minded. When you close your mind than you stop learning; that is what Choi did in my opinion.
"IF I COME ... I'M BRINGING THE PAIN WITH ME"