Unfortunately this neither solves the problem nor explains it. It USED TO be supported because I used to use this feature daily. Controlling a keynote presentation with the iPhone came in handy. But I can no longer do that because the devices will not pair, and thereby I cannot use the phone to remote control keynote files. Moreover, Apple seems to have done a remarkably bad job of making such pairing options intuitive through connections other than Bluetooth.
I am still awaiting a solution for beneficial features that worked perfectly well within outdated systems but DO NOT work with these "upgrades."