Custom visual matrix dataview sorting behavior

[john_m_dixon]

I have a custom visual that uses a matrix dataview. I have sorting set to ascending on a numeric column, but I am seeing odd behavior in the "sorted" dataset. The data is hierarchical, but the column being sorted on does not roll up to all levels of the hierarchy, as it is only applicable to the lowest level. 

In this case, I am sorting on the right-most column, StageOldAge.

I would expect Jurassic to be above Triassic in this case becuse Tithonian (152.10) is less than Ladinian (242.0).

Not sure if this is because the StageOldAge column does not roll up in the hierarchy, and these values are blank. Sorting is respected at the lowest level of the hierarchy, but the order at the higher levels seems undefined.

Is this expected behavior? In this case I'm disabling user sorting and defining custom sorting in the visual.