Apple has barely released iOS 13, but you might be getting another significant revision mere days later. The company has told Engadget it's moving the releases of iPadOS and iOS 13.1 to September 24th, or nearly a week before the originally scheduled September 30th debut. While there's no mention of just why Apple is stepping up the pace, it might be due to software stability. Some iPhone 11 reviewers (including Engadget) have noticed buggy behavior in iOS 13.0, and this could iron out the kinks before there's been too much opportunity to complain.
You will get some new features in return. iPadOS, as you may know, is a major shake-up that introduces more iPad-specific features, such as better multitasking and a widget view on the home screen. The iOS 13.1 update mainly adds features that didn't make the cut for 13.0, including ETA sharing in Maps, automated Siri Shortcut actions and data separation for enterprise devices. This definitely isn't a seamless release, then, but you at least shouldn't have to wait long to see new features and a smoother overall experience.