My teacher, the late Gayle Fillman, often ended throws in this position and while during the time I trained w/ her she never specifically instructed us to do so for that or any other reason, I know that the idea of the spiral and balance between heaven and earth was important to her.
Interesting. I have never told or mentioned that anyone else should do it. In fact I never even put any significance on myself doing it. Only David mentioning it like he did above made me wonder if I had seen anyone else do it.