Feels like UI elements have a lot of abstractions that are not perfect for motions. With every hack you work around the layout engine that gives you this simplicity of defining layouts. Some libraries allow you to define keyframes for the motions in between, but it still isn't perfect, especially if you look at the youtube sample where one element overlaps the other and the animation would take up too much time or look odd if this wasn't the case. Even if you perfect all of this, would you really want to spend more processing power and script weight on these aspects? I feel like most UIs have severe latency issues out of the box, anything that doesn't address the elephant in the room adds insult to injury.