Here's a picture that helps explain what's going on.
https://aegisacademy.com/schedule/trajectory/
The bullet starts out below the sights. Gravity begins acting on the bullet the instant that it leaves the bore.
The bullet will be driven upwards by the upwards angle of the bore relative to the sights and its trajectory will carry it up to the level of the sights, and then above them. The bullet will cross the sightline twice. Once going upward and once when the upward velocity imparted by the upward angled bore is finally overcome by gravity and the bullet starts falling back downward.
When you zero a rifle at very close range, you're adjusting the point of aim to align with the point of impact for the point where the bullet is crossing the sight line on the upwards part of the trajectory.
As a result, it will keep going upwards for awhile and you will find that your point of impact rises on the target as the range increases. Eventually gravity wins and the bullet will come back down, crossing the line of sight somewhere far downrange.
Anyway, all of that to say that, at most, the bullet only hits the target perfectly aligned with the sights at two ranges. At all the other ranges, it's a compromise.