Finding and your answer
Account.AccountGroup column
Not found in this gold boundary
99%
How the model read it
The authoritative register requires an Account.AccountGroup management roll-up. The audited Account inventory contains AccountKey, AccountName and AccountType only; no AccountGroup object is present in available current gold.
Workbook evidence
Cited current gold
Open questions
What is the authoritative source and owner for AccountGroup mappings?
Can an account belong to more than one management group, and are mappings effective-dated?
The reference examples differ in grouping vocabulary from some chart-of-accounts examples; what controlled hierarchy is intended?