most of the time if you (re)open an app and you get "an image of the screen of what you were doing last" for half of a second before it refreshes itself and changes slightly! you guys know what i mean right? i thought this was a 4s thing but i tried on the 5 and the result was similar... what is this? come on apple test it yourself: open contacts, scroll down, while scrolling down quickly hit the home button and relaunch the app! ios6 didnt have this issue!
this is an energy saving feature. no need to refresh the UI of an app when it's not even visible. thats why it saves the last known state and only refreshs when its open. when you close the app while scrolling it just saves the last shown state. your example is kind of proof, that you have to force it to happen.