Duplicate of MC-10168

What I expected to happen was...
Throwing a Lingering or Splash Potion of Regeneration at a Zombie, Skeleton, Wither or other mobs considered "undead" would poison them, similiar to how the Instant Health potion harms them.

What actually happened was...
The health of the target mobs didn't change.

Steps to Reproduce
1.

/summon WitherBoss

2.

/summon Zombie

3.

/summon Skeleton

4.

/summon PigZombie

4.

/give @p splash_potion 1 0 {Potion:regeneration}

5.

Throw the potion at the spawned mobs

Extra: Observe the Wither's health bar to note that the problem isn't in the animation, but in the mobs actually not losing health due to the potion. Instead, their health is increased just as usual.