Something interesting in the video above: at 8:30, when he plugs the headphones into the headphone jack (on the iPhone SE), there’s a small Music app icon on the screen right where the headphone jack is. I’ve never seen that icon before when you plug the headphones in. I just tried it right now, and nothing.
Is it something new in iOS 9.3.1 (I’m still on 9.3 and not in a rush to update)?