ORIGINAL: mauser06
im going to have to say.....myth!!!!!
ive shot a random variety of fixed heads, fieldpoints, and mechanics from the same bow on different arrows with the blades oriented in random ways...i still hit where i should have.
the key is having your bow tuned well enough to shoot fixed heads...and having enough fletching and a good offset or helical to help steer the arrow..
exactly this is a myth that they have to be in a certain position but many will line them up just because it looks cool and it won't hurt the flight.