Mobs are able to track players/other mobs through diagonally placed blocks

The bug

Mobs are able to track players/other mobs through diagonally placed blocks.

How to reproduce / Example

1. I made a little encasement for zombies, as you can see in picture 1. It has diagonal blocks.
   
2. In picture 2 you see a villager on the outside of the encasement and all the zombies try to get to him.
   
3. In picture 3 you seen another villager inside the encasement, they don't seem to be interested though.
   
   → They shouldn't see the villager on the outside only the one on the inside.

Affected mobs

• Ocelots and chickens
• Llamas and wolves
• Wolves and skeletons
• Wolves and rabbits
• Wolves and sheep
• Villagers and evokers (not vindicators however?)
• Iron golems and evokers