Shulkers spawning inside chain related blocks

To replicate the glitch:

1. Go to an area where the shulker has only the choice of teleporting on the block its on

2. Spawn a shulker on the block you placed

3. It will teleport within the block as seen in the image

This works on end rods, chains and lightning rods which all have similar hitboxes which I would guess is the issue.