I noticed that when in fullscreen cover view there's a strange line at the top. Noticed that on my iPhone X and iPhone 5s. Did NOT see it on Android.
First I thought I had a defective line of pixels on my iPhone X ...
Nothing major of course but I don't think this is intentional behaviour. See screenshot from my iPhone 5s attached. Btw you can't really see that line when there's a white background like on this page.