Hitbox of 3 walls too high

The hitbox of walls is too high. I don't mean the collision box. The collision box is 1.5 blocks high which is correct. But the hitbox which is the outline that you see when looking at it is too high when having 2 walls next it.

How to reproduce:

1. place 3 walls next to each other.
2. Look at the wall in the middle

You see that the outline is higher than the texture.