Hyper Tree Grid does not have Ghosts cell structure
I don't think there was an issue on that.
vtkHyperTreeGrid does not have ghost cell structure for multi-processing. One would need ghost hyper trees so filters using super cursors can reach hyper tree interfaces with other processes.
A filter that needs this feature is
vtkHyperTreeGridContour filter. Right now, when applying this filter using MPI, cells at the interfaces are discarded.