The bug

Knockback dealt by wind charges is different depending on where you hit an entity. The closer to the feet you hit them with the more knockback they will take.

Steps to reproduce:

1. Throw wind charges at any entity such as a zombie or a player at its head and feet
2. Notice how it takes more knockback if its feet is hit by the wind charge 

Intended behavior

The knockback should be consistent no matter what

Actual behavior

Hitting the feet of the entity makes them take more knockback