That looks like the HDD is connected to the USB stick
Edit: looking again at the more complex picture, I understand that this shows the folder structure; that might be confusing for people coming from Windows; not sure if it would be better to show the physical structure instead of the logical one.
And I would suggest to use a symbol that is indicating an SSD instead of an HDD (have to admit don't know how such a symbol looks like)
I think this is a good idea to have a simple setup first and then the more complex setup to explain certain considerations.
Let's see what geoffwhere thinks.