Given how high the shooter had to aim, the bullet would have been coming down at an angle.
It's not actually that bad. While the drop makes the elevation sound impressive the stated angle of 327 arc minutes is 5.45 degrees. To put that into perspective it's about the long edge of a business card at the distance of a meter so while considerable it's not exactly a lob. Judging from the drop of at 3700 and 3800 yards the downward angle would only be in the range of 10 to 15 degrees depending on the actual BC of the projectile.