The notch in the iPhone X’s screen is a problem for many app since it is an element that should not be found on a rectangular screen after which the applications are made.
So Apple does not want iPhone X users to be bothered by the cut in the screen, that sometimes block the content and demands developers to do their apps so that all new apps should support the iPhone’s special display.
“Starting April 2018, all new iOS apps submitted to the App Store must be built with the iOS 11 SDK, included in Xcode 9 or later. All new apps for iPhone, including universal apps, must support the Super Retina display of iPhone X”, said Apple to the develepers.
In other words, you want you apps in the App Store for iPhone, it has to be compatible with the iPhone X’s iregular display. If “notch”, your app may “notch” be allowed in App Store.