Nothing is actually faster. The transitions have improved making everything feel more fluid. In fact I think app open times are slightly slower!
The app open times aren't slower. You're just presented with the blank app screen while it loads sooner because the animation to get in is faster. So because you see the blank screen while it loads for longer, you think it's taking longer to load. When it is the same. One of the purposes of an animation is to mask the app load time.