If you stun a mob, even from behind - they will turn to face you no matter which direction you stunned them from, or even if you stun them again.
This is not the case on the live client, as when you stun them there they will face the direction they were already facing, instead of facing you.
Here are two gifs comparing them, one from the old client and one from the new client:
The mob turns to face me even though I stunned it from behind, and turns again when I stun/attack it for the second time:
You can see the mob faces the same direction he was first stunned in, and continues to do so when I attack him again: