Thanks Mark! I totally agree that this should be made more explicit. It is important to remember that there is a whole bunch of information being thrown at a student who is learning to program for the first time: how the interface works, how interpreted languages work, how computers work, the syntax of the language, the vocabulary of the language, the result of evaluating the language, .... Yikes, it even overwhelms me! Make sure there is a solid foundation in something, I think the interface is the simplest domain over which a student can gain mastery, this builds on the positive psychology concept of the Zorro Circle from the Happiness Advantage.
Beyond having the kids read the first section, it is really great if you can find a way to enact the group activities described in the TEACH cells (switch to TEACHER display mode to see them). These activities are designed to engage children's preexisting knowledge about relationships. Scaffolding programming concepts on top of this type of social knowledge through analogy with human relationships can be far more effective than simply exposing kids to technical descriptions and definitions. A big shout out to Anna Musser who helped me develop the activities and taught me all about scaffolding STEM concepts on top of children's preexisting social knowledge.
I am also very proud of the fact that kids can simply click on the CODE tab of any CODE cell to evaluate the Wolfram Language within it. There is a surprising amount of cognitive load required for kids to remember to simultaneously hold SHIFT and press ENTER. Removing this cognitive load by providing a simple button seems to increase the ease of use substantially. With the current style of the notebook the only way for kids to learn this trick is by doing the first section of the tutorial.
There is a proliferation of complex and diverse software interfaces, and I always start teaching any software with the basics of how to interact with the interface. I even do this for introductory Mathematica seminars at advanced institutions like MIT. It seems to relieve a lot of stress when people understand the different functions of the frontend and the kernel. People seem to be more comfortable with well-defined roles and responsibilities.