I definitely agree that chidori nagashi is a technique similar to Neji's Kaiten. Because it is most likely developed from the original Chidori technique and extended to cover the whole body, I have developed some interesting theories. Perhaps, since Naruto and the others were simply knocked back, it is just the same amount of chakra employed in the original Chidori but more spread out and released simultaneously from all of Sasuke's tenketsu rather than just the ones in his left palm.