Same guidelines also specify the safe area to put actual content, which excludes that area. In addition they suggest not hiding the status bar, which generally

Same guidelines also specify the safe area to put actual content, which excludes that area. In addition they suggest not hiding the status bar, which generally would push your content below it anyway. > Inset essential content to prevent clipping. In general, content should be centered and symmetrically inset so it looks great in any orientation and isn't clipped by corners or the device's sensor housing, or obscured by the indicator for accessing the Home screen ...and... > If your app currently hides the status bar, reconsider that decision on iPhone X. The display height on iPhone provides more vertical space for content than the displays of 4.7" iPhones, and the status bar occupies an area of the screen your app probably won't fully utilize. [emphases mine] My take is they don't want you putting a black background up there to mask it (unless all of your background is black, presumably) but you don't have to lay out around it either. For videos and photos in particular, since black is the normal background for outside the image I doubt there'll be an issue using it at the ends.