And they’ve got a point. Fragments are ViewControllers (excluding “retained headless”), so why create a ViewController just to host additional ViewControllers in it?
We do believe that this focus on declarative motion specification will simplify creating such animations, as well as open the way to provide great graphical tooling in Android Studio.
MotionLayout was created to bridge the gap between layout transitions and complex motion handling. You can think of it in terms of capabilities as a mix between the property animation framework, TransitionManager, and CoordinatorLayout.