When creating a new client the Chart of accounts (COA) importer does not import summary accounts.
Steps to reproduce:
Create a new client with the "Intial client" setup. Select the 'AccountingUS.csv' as the COA definition file.
Login to the new client as admin.
Go to the "Import File loader".
Select the "AccountingUS.csv" file to load.
Select "Accounting - Accounts" as import format.
Import the file.
Go to "Account element".
See a hierarchy (tree) of accounts with accounts having summary accounts above them. Just like in GardenWorld.
A flat list of detail accounts (account numbers with 5 digits) and all summary accounts missing.
Fixed the issue by buying a pair of glasses and drinking a cup of well caffeinated coffee. In other words it was an user error on my part.