So by your logic there are two outcomes.
1. Fixed amount of bullet drop always makes it land in same area
2. Bullet drop is totally ignored and bullet goes straight to target.
With no bullets anywhere in the massive amount of space between the "splodge of misses" and the "hits".
Sounds to me like the game works out if its a hit or not at the time of firing, puts a "hit" or "miss" flag on said bullet and then applies bullet drop to the misses.
Otherwise you would see "random heights" and "random amounts of bullet drop" the entire length of distance between shooter to target, which you dont.
This is the system we run to and have had perfectly fine results in Linebattles for over a year now at any distance shooting we decide to engage at, Point at target, pull trigger, job done.
So even if it isnt exactly spot on nobody else has come up with a demonstrable test to prove otherwise and the results speak for themselves. Your "small chance" of hitting the target isn't all that small at all if it wins line battles comfortably.