Reinforcement zombies are not centered on a block

The bug

Zombies spawning as reinforcement are not centered on a block, instead they use are spawned between 4 blocks.

How to reproduce

1. Set the difficulty to "Hard"

   /difficulty hard
   

2. Set the gamerule doMobSpawning to true if it is not already

   /gamerule doMobSpawning true
   

3. Set the time to night or make sure there is no light in the area around you

   /time set night
   

4. Setup a repeating command block with the following command

   /execute as @e[type=zombie] run attribute @s generic.movement_speed base set 0
   

5. Summon a zombie using the following command

   /summon zombie ~ ~ ~ {Attributes:[{Name:"zombie.spawn_reinforcements",Base:1.0}]}
   

6. Hit the zombie a few times
7. Search for the spawned reinforcement zombies

   /effect give @e[type=zombie] glowing
   

   → You should see that the zombie is not centered on a block

Code analysis

Based on 1.11.2 decompiled using MCP 9.35 rc1

The method net.minecraft.entity.monster.EntityZombie.attackEntityFrom(DamageSource, float) does not add 0.5 to the X and Z coordinate it uses for spawning the zombies.