If you fletch up a dozen or more arrows, and number each in sequence, then start shooting each arrow at random (no particular order), and record where each hits in the target; you will find the same arrow hitting the same area (spot) with predictable results.
Another way is to draw a cross through the target, and record the hits according to upper right, lower right, lower left and upper left. The objective is to keep the groups separate when you shoot. This does require consistent and accurate shooting at reasonable distances.
I believe there are differences in the materials from one arrow to the next, even with aluminum or graphite. It also explains why, some arrows go where you are looking, and others don't. The objective is to shoot them as a group especially when hunting. Mixing groups will result in more misses. Arrows that don't group, might shoot okay in another bow.