Interesting that they added this, specially as a supported feature in iOS - I wonder what is the use-case they want to support..
Now, with that said - this is not really new - there's been ways to record the screen on Android and iOS, but they weren't easy.. Android for example required you to either install an app (which came way later) or enable developer mode (which is a hidden setting), then pair the phone with a computer and use the debugger to run the built-in screen recorder software..