Nostalrius Begins - Quality wow vanilla realm (1.12)

When I made a rogue, I noticed that hostile mobs of my own level didn't do what they did in retail vanilla when I moved into the far reach of their peripheral; stopping, looking at me, making an aggro noise, but not actually aggroing unless I continue to move into their view. I imagine anyone who's been perceptive while playing a stealth class in retail at any point in its life knows what I mean.

Am I lagging and being considered still moving in their view, so it foregoes the suspicion mechanic? Or is it simply not present? If so, is it a known bug?

I have seen the same thing happen over and over. I can actually only recall a few times where the "suspicion" animation work properly. Until I had saw it work I assumed it was not in the game. So my guess is it is bugged/broken; no idea if it have been reported to the proper channels.

I've played rogue for 4 months here now and I never saw the mobs doing this.
Bugged or not implemented.

Seems like it's not implemented, which is sad.