From macrumors.com
While no other details were provided, it was assumed that the update added support for recently released devices, including iPhone 13 models, the new iPad mini, and the ninth-generation iPad. Still, the update was the first of its kind to come through System Preferences -> Software Update, which made some users curious about it.
Usually when you connect an iPhone, iPad, or iPod touch to a Mac, a dialog pops up from an app called MobileDeviceUpdater that says “A software update is required to connect” to your iOS device. This normally happens when the device has been independently updated with a newer version of iOS or iPadOS that the Mac doesn’t recognize, indicating that the download is required for your Mac to communicate with the device.