Hi @rmisuraca,
The goals of Unit 4 include “consider and understand the needs of others while developing a solution to a problem” as well as “prototype solutions both on paper and in App Lab” (from the CSD curriculum guide). So, Unit 4 introduces students to App Lab on a very introductory level with the intent of creating a digital prototype of their app and not a fully functioning app. Student go deeper into App Lab in Unit 6 and even deeper if they continue with computer science and take Computer Science Principals, usually taught in high school. I hope this clarifies the introductory nature of Unit 4.
Michelle