Where are the Delta updates in iOS6?

I've read about many articles where people said that in iOS6 their app updates take faster than usual. However, I'm not experiencing this.

Apps like Real Racing 3, Subway Surfers, etc etc still take very long to download (most likely the same time it takes to download the app just after purchasing them).

In fact I think they download the entire application. What gives? Perhaps they haven't implemented the delta update system?