I read somewhere (I think Jim Hamm's book, Bows of the Native Americans) that you use the larger/ground end for the nock. The rationale was that if you have one of those pesky bends that keeps coming back after straightening, it tends to happen higher on the shoot, and you don't want one of those under the fletching. I have a bunch of shoot shafts I am going to try hard to turn into arrows this summer, and I am using the larger end for the point since I like the weight forward aspect. I guess you could use larger shoots and plane them down with a reverse taper...that seems like an awful lot of work though.
Sorry to continue to wander off topic from the original post...I have wondered that about bending green wood too, and don't have a good answer.