Shulkers can occupy the same spaces as some non-full blocks

The Bug:

Shulkers can occupy the same spaces as some non-full blocks.

Steps to Reproduce:

1. Build the setup as shown in the provided attachment. setup.png
2. Obtain a shulker spawn egg and attempt to summon shulkers within the same spaces as the fence gate, fence, and torch.
3. Observe how the shulker briefly occupies the said space before teleporting away.
4. Take note as to whether or not shulkers can occupy the same spaces as some non-full blocks.

Observed Behavior:

Shulkers can occupy the same spaces as some non-full blocks.

Expected Behavior:

Shulkers would not be able to occupy the same spaces as some non-full blocks.