Often you need to change some small things in your admin theme. The right way to make it is to inherit everything from the admin theme you want and do your changes in a sub child admin theme.
The idea is though not just to be another platform with some boring videos but all the videos to be inspired by real-world problems. That means something that you will most probably need if you work with Drupal. We want you to be successful and we want to teach you everything we know about Drupal!
So watch the videos, try to follow and reproduce, ask questions and you will see you will be able to conquer this wonderful sea that Drupal 8 is.