They were shooting in England for months. I wonder if anyone went to the set and offered their services on how to properly shoot a warbow, knowing they would do it wrong. This was also 12th-13th century, do we in fact know that bows were pulled back to the ear during this time, even amongst yeomen hunting or robbing in the forrest?
I saw Orlando Bloom firing a bow in one of his movies, I think it was Troy, and he was drawing it back pretty far, but it *looked* really ugly. The producer/directors probably thought the same. Who knows