MDAC 2.5 SDK - OLE DB Programmer's Reference
Chapter 23: Rowsets in OLE DB for OLAP

Order of Members in a Flattened Rowset

The order of members in a flattened rowset is the same as the order of those members in the axis. In other words, member order remains invariant during the flattening operation. Level transitions on an axis appear on different columns, thereby nesting the values.