iBooks on iPhone 5 shows black bar on top

I understood that Apple have adapted every single app of their own to the wide screen on the iPhone 5, but I am seeing that iBooks make dissapear the cell operator, the clock and the battery level icon, but that part doesn't go to white, making it the "full screen" theme. And it really disturb me.

Is it a bug that will find solution in next app update? Happens only to me?