You are forgetting two importance things here. One, the archer does not
have a crosshair that he puts slightly above the window. He is going
mostly by feel and experience. I shot quite a few arrows when I was of
the age that does that, and as skill builds, the arrows know to find
their target. The archer is not moving dials or crosshairs.
So what? He's still *aiming*.
I don't know if you did proper archery, as I have, or just played around
with a toy bow with rubber arrows, but it's only in fairy tales that
there are magic arrows that "know to find their target". The archer may
not be able to articulate all the factors involved, but you can damn well
bet that "aim a little bit higher than the target" is one of the factors
that he could consciously say.
("A little bit" is naturally dependent on how distant the target is.)
They weren't idiots, and even in the Middle Ages if you aimed directly at
a distant target your arrow would drop below where you were aiming.
The second thing that you are forgetting is that archery skills are a
classified military information. Should one develop a system for
improving accuracy, he would not tell it to everyone.
What a load of bollocks.
Far from archery skills being a "military secret", archery was a common
skill amongst both the nobility and the commoners. Nobles hunted game;
even ladies sometimes hunted small game like rabbits. Professional
hunters used the bow to feed themselves and their families. People
learned to use the bow from childhood.
In 1363, England's King Edward III declared that every able-bodied man in
the kingdom, rich and poor alike, must practice archery at holidays and
other opportunities. Archery skills weren't a secret known by a few, they
were extremely common. In modern terms, don't think "knows the codes to
launch the nuclear missiles", think "knowing how to aim your rifle at a
target and pull the trigger": even the guys sitting out the war behind a
desk are expected to know how to shoot a rifle. In some battles, English
armies were made up of up to nine archers out of every ten fighting men.
A skill that common was no secret.
The overwhelming military advantage England had over the French was the
hardware and tactics: the Welsh longbow was a formidable weapon, far more
powerful than the European bows, and the English nobility relied on it
while the French treated their peasant soldiers with contempt. The
English lords might have been just as contemptuous of their archers'
social class as the French were, but they had nothing but respect for the
power of their weapon. The French archers were simply outgunned, or
outbowed if you prefer, and the French knights were brave but stupid.