https://www.theverge.com/2017/10/9/16447742/apple-ios-11-notification-center-iphone-guide

One of the larger changes in iOS 11 is the Notification Center, which has been overhauled yet again on Apple's new mobile operating system into a somewhat confusing design.

Apple is taking a different — we'll charitably call it "unique" — approach to notifications in iOS 11. Under Apple's logic, notifications live on your lock screen, where they pop up for you to address as they come in. So why not make your Notification Center more like the lock screen? In fact, why not just make them one and the same?