Reflecting a blue skull does not paralyze the wither

In previous versions, when you deflected a blue skull fired by the wither towards itself, it would freeze for a few seconds (which was intentional). Now this mechanic does not work.

Steps to Reproduce:

• Summon a wither. 
• Give you regeneration of high lever and change your game mode to survival. 
• Wait for the wither to shoot a blue skull at you. 
• Hit the blue skull in a way that hits the wither back.

Observed Results:

The wither continues moving and attacking.

Expected Results:

The wither should "freeze" for an instant when hit by the blue skull.