Zinn reckons it's do with the SRAM jockey wheels, but Schleck uses the modified varsion as designed by Wolfgang Berner
Not always.
"(However, if Schleck was using this upgraded version, that loop might not have been there, and my theory may have a huge hole in it. But the video is inconclusive whether he has this cage [I actually think the beginning of the video with the mechanics shows the loop], and you’ll find plenty of photos online from the Tour showing unadulterated Red rear derailleurs on various of Cancellara’s and Schleck’s bikes, save for special painting – yellow for the yellow jersey, or gold for Cancellara’s world and Olympic medals.)"
Not always.
"(However, if Schleck was using this upgraded version, that loop might not have been there, and my theory may have a huge hole in it. But the video is inconclusive whether he has this cage [I actually think the beginning of the video with the mechanics shows the loop], and you’ll find plenty of photos online from the Tour showing unadulterated Red rear derailleurs on various of Cancellara’s and Schleck’s bikes, save for special painting – yellow for the yellow jersey, or gold for Cancellara’s world and Olympic medals.)"