This happens after I update my iPad to iOS 12. When I remove an app from my device, it seems that the app isn’t removed immediately.
More precisely, when I redownload the app from App Store, usually the progress indicator will be slow enough for me to see the download progress. I do have a fast Wi-Fi access, so I can download things in e.g. 40Mbps (so 5MBps), and I expect to finish downloading a 50MB-app in around 12-15 seconds (some extra time for installation). However, when I redownload an app shortly after I removed it from the home screen (it was removed, at least not appearing at Settings -> General -> iPad Storage), the app reappears almost immediately. There is no “Loading...” or “Waiting” label showing in the home screen. Instead, a greyed-out icon appears after I redownload the app from App Store, and then it changes to a normal bright one shortly.
Just for curiosity: is this a bug or a feature?