I have no idea, but a wild guess is that with old hardware the "hot" pixel that could trigger the collision interrupt was fixed to the upper left corner of
the hardware sprite.
EDIT: Another thought that crossed my mind is that with very lo-res screens a corner is the only way to get a well defined and sharp (yet fairly wide) arrowhead. The trade-off would be the shaft being pixelated, but the tip is more important.
EDIT: Another thought that crossed my mind is that with very lo-res screens a corner is the only way to get a well defined and sharp (yet fairly wide) arrowhead. The trade-off would be the shaft being pixelated, but the tip is more important.