Those codelabs and the website were originally designed for on-site experience where you can sit down and try something new without the need to bring your own laptop or another piece of hardware and set up the environment.
In fact, I'm sure anyone who's been to I/O event in person noticed quite a few friendly faces and field experts to talk to in the codelabs room. Often, they are the same people who wrote the actual codelabs.
Then we thought, why not make these codelabs public for people to also be able to try it at home. So, there it is, inhuman codelabs.
Thanks for the feedback! I dislike the ripple animations, too. This is coming from Material design implementation in Polymer components 1.0.
Hijacking navigation wasn't very nice either, absolutely agree. Too bad we didn't have time to drop it.
All of this is going to be replaced soon. Codelabs site is moving away from Polymer. Working on the new implementation in https://github.com/googlecodelabs/codelab-elements. Contributions are most welcome, of course.