iOS 9.1 vs iOS 9: What’s New in iOS 9.1

Support to Set Up New Apple TV

The new Apple TV release date arrives on October 26th online and if you want to set up the new Apple TV using your iPhone you will need to install iOS 9.1.

Apple notes that users who want to set up the new Apple TV with an iPhone will need to use iOS 9.1. It's not immediately clear why you need iOS 9.1 to set up the new Apple TV, but it does connect the update to the Apple TV.