They meant if you close it and, say, want to read or follow along with a book in iBooks and not use split view, you have to multitask back to Prompt every 3 min

They meant if you close it and, say, want to read or follow along with a book in iBooks and not use split view, you have to multitask back to Prompt every 3 minutes or iOS will suspend the app, killing your SSH connection in the process. Since Prompt is closed source and on the App Store, they can't use mosh which solves this problem.