It's a nice theory but it only works if the animations are smooth and designed to improve understandability. The vast majority of UI animations are pure visual

It's a nice theory but it only works if the animations are smooth and designed to improve understandability. The vast majority of UI animations are pure visual flourishes that take twice as long as they should and don't make any kind of sense spatially or physically or improve the user's understanding of what's happening at all. There's a lot of cargo cult UI design out there. And what's worse is that most of the animations either don't start at the initial state of the UI or finish at the final state, or perform so badly that they hardly show any frames in between, so you have the worst of both worlds: abrupt jerky transitions and wasted time. UI transitions that make spatial sense, are fast enough, are fluid, and don't slow down typical use of the UI are rare unicorns.