Unlike person document in the public name & address book, the person form in the personal name and address book does not have a field to enter corporate hierarchy level.
Therefore, when you open ($PeopleGroupsCorpHier) view in your PAB, the registered contact information categorizes under
"*No Corporate Hierarchy Specified*", nevertheless, when you click on the "Address" button from memo form, it still has the ability to display PeopleGroupsCorpHier view in your PAB.
Moreover, when the user have huge number of contact information registered to their PAB, the ability to categorize under Corporate Hierarchy level is quite essential.
*By obtaining contact information from the NAB with those person documents that has the corporate hierarchy level specified, the registered contact information will successfully be categorized in the PeopleGroupsCorpHier view. Though, this is not the issue