I just upgraded to iOS 12 and now when watching videos that aren't full screen on the iPad's 4:3 screen, the double tap to zoom in on the video feature doesn't work anymore. Did they completely remove this function? You can still manually zoom by doing a pinch-to-zoom function but that only works as long as you hold your fingers on the screen. Is the removal of this feature related to how iPhone apps on iPad don't fill the screen up as much anymore?