I did this course last year and just checked my notes and they are the same - you set up customers and suppliers, and then never use them.
I think the reason is to show how to set up them up before you need them (Task 2) and then to show how to set them up as you enter the invoices.
The customer address list I sent just had the 4 from task 2,
The customer activity report (Task 5) had all. but the original 4 showed no activity.