Can walk through piston arm if piston placed facing east (f = 3)

In both gamemodes, placing a piston while facing east then powering it will allow you to talk through the piston head.
Walking through these piston while facing north makes the heads act as if they are a full block, meaning you can't walk to the piston arm itself.

What I expected to happen was...:
What happens when the piston faces any other direction, you cannot walk through it.

What actually happened was...:
You could walk through it

Steps to Reproduce:
1. Face EAST
2. Place any kind of piston, one on top of each other
3. Power both pistons in any way
4. Face the arm from the south
5. Walk southwest so you are stuck between the arm and head of the piston
6. Walk southeast into the piston head