Audi and everyone:
I think that some (not all) of the pivots and turns were included by the masters of old not for specific martial application, but principally to train agility. But I have an actual experience that I would like to relate. My first teacher, Sifu Al Bender, is not a traditional Yang stylist; he teaches Guang Ping and Northern Shaolin. I enjoy playing freestyle with him; because his roots are in Shaolin, he's extremely aggressive and tests my (meager) neutralization skills to the max. A couple of weeks ago, we were playing and he moved forward with a quick and aggressive hand technique aimed at my midsection. I stepped on a lateral line to my left, looking to take control of him from behind and maybe apply a press to him on a line of weak resistance. When he sensed my movement offline, he stopped on a dime and pivoted around on the ball of his left foot with left hand extended in a reverse split/strike - the mirror image of the pivot immediately preceding sweeping lotus kick in the 103 form. I agree that generally it's not a good idea to turn your back on an opponent, but in this case, I was already moving behind him. Because the strike originated in front of him, and his body was shielding my vision, I did not see the strike coming, so fortunately he had the control to stop short. It was quick and surprising, and, most importantly, it worked. As we analyzed it later, I came to the conclusion that, given his position and momentum, the strike he used was the most efficient line of attack at the time. I don't study Shaolin, but I have performed parts of the 103 for Al, and he says he can really see Shaolin roots in many of the movements. He also said that the pivot he used is very common in Shaolin. So while I would earlier have dismissed the pivot as pretty but generally impractical, now I'm not so sure.