Mobs can embed inside wall blocks and do not take suffocation damage

Steps to reproduce:
1. Create a new flat creative world, no resource packs, no mods.
2. Place cobblestone wall blocks.
3. Spawn a small mob (baby chicken / baby cow) next to it, push the mob into the wall block.
4. Let the mob stay embedded inside the wall block.

Expected result:
When a mob's hitbox is inside a solid block space, it should receive suffocation damage and eventually die.

Actual result:
Small mobs can stay embedded inside wall blocks permanently. They take NO suffocation damage.

Platform: Windows
Game mode: Creative
Singleplayer, vanilla only.
Tested mobs: baby chicken, baby cow