Tweetie 2 simply took this idea from Tweetie 1, that reloading was simply “loading newer”, and “loading newer” put new messages at the top of the list… and activated the action based on a finger motion that you were already doing. Why make the user stop scrolling, lift their finger, then tap a button? Why not have them continue the gesture that they are already in the process of making? When I want to see newer stuff, I scroll up. So I made scrolling itself the gesture.