I agree that the two chapters would be best lumped together compared with being lumped into any other unit. In terms of more specific commonalities, I'd say both chapters focus on the "handling" of data. Neither chapter is fundamental to the basic workings of the internet (which distinguishes Unit 2 Chapter 1 from Unit 1 Chapter 1), and neither chapter is as relevant to the programming concepts in the programming-related units.
Looking at things really broadly, I'm trying to boil down each unit. Here's my interpretation:
- Unit 1 in a broad stroke is about communication. How do we communicate to one another using the technological tools we have, and how do we build systems upon it to enhance our ability to communicate?
- Unit 3 is about building. How do we use computers to create? How do we "talk" to computers so they understand us? What are tools that allow us to build what may be more difficult to build in person?
- Unit 2... is about interpreting. How do we take the "digital" and turn it into "information" (and vice versa). Chapter 2 asks how do we collect and organize large masses of data and take that data and make it meaningful (find patterns, tell a story). Chapter 1 asks how do we take human experiences and translate them into "computer", and back (and how to do it efficiently). Loosely, the unit is about the translation between "computer" and what's meaningful and useful to humans.
All 3 units definitely share some overlap though. That's my take on it.