I don't know if this counts for anything but when i was very little i made a little stickbow, had no tiller because i knew nothing about bows other than the stuff from my Dangerous Book for Boys book. When i made arrows i knew that people used three fetched arrows normally, and i tried to, but my little brain told me that it was too hard and that there should be no difference between two fletch and three fletch. as long as the back of the arrow wants to move slower than the front.
I think if a little 6 yr old can figure out that much without knowing anything about bows, other people back then knew about it too. My hypothesis (yes, getting fancy
) is that the three fletch arrow is like having a fluted hunting point, or decoration. Its not necessary but maybe it shows that you put more effort into it... or maybe its just tradition... probably is just tradition lol. (I am probably over analyzing an extra feather)