I spoke to Apple today and they told me that this "airplay without mirroring" functionality has been disabled in iOS 11. They noted that, once you upgrade to iOs 11, you can only "airplay content without mirroring" if the app you are using to project the app from your IOS device onto your TV is airplay-enabled. You will know if an app is airplay-enabled if you can see the airplay logo within the app. All of the big players (Netllflix, Hulu, Amazon, etc...) offer this functionality. But, if you want to play something on safari that does not have this functionality, you can longer stream it on your Apple TV without turning on "screen mirroring" until and unless the operator of the app/website updates its app/website to enable native Airplay functionality. Super annoying as you can't do anything else with your ipad while you have screen mirroring on. I have decided not to upgrade to iOS 11 on any of my other devices and am exploring various apps that may help fill the gap that Apple has created here.