Further investigation into the issue has revealed that HiearchicalHeaderView re-implements the header views sections, and there is no relationship between the QHeaderView notion of sections, and the HiearchicalHeaderView notion of sections.
As a result, the following calls are available, but return incorrect data.
QHeaderView::count() returns 0
QHeaderView::sectionSize(int) returns 0
QHeaderView::logicalIndex(int) returns -1
etc...
The upshot of this is that there is a significant amount of work required in HierarchicalHeaderView in order to make in feature complete, and that the way it is currently implemented is not symbiotic with QHeaderView
That essentially leaves 2 questions.
Does an open source feature-complete hierarchical header view exist?
Is there a way to easily implement hierarchical headers in a QHeaderView?