2.1.791 Part 1 Section, rowHierarchyUsage (Row OLAP Hierarchies)

a.   The standard does not specify that @hierarchyUsage values cannot be duplicated.

In Office, @hierarchyUsage values may not be duplicated within a rowHierarchiesUsage.

b.   The standard says hierarchyUsage specifies the reference to an OLAP hierarchy in a PivotTable.

In Office, @hierarchyUsage must be -2 (specifying the data hierarchy) or greater than or equal to 0 and less than the number of pivotHierarchy elements.