This is just a description of the observed behaviour, I have no knowledge of how wmf files actually work.
Here:
https://answers.launchpad.net/inkscape/+question/455387
a user asked a question about wmf import being messed up.
It appears that:
- colored rectangles that make up the columns in the diagram are missing
- the stroked rectangles, that make up the borders of the columns, have undergone a 'stroke to path' procedure
- the markers on the columns' tops have a very strange size when selected with selection tool (as big as the whole column). They consist of one more node that I cannot find. When editing them with the node tool, their size goes back to the visible size.
If I take a detour and import the wmf file into LibreOffice, and then export as pdf, and import the pdf into Inkscape, the drawing is usable and complete, with some additional strokes on each column (split apart for each side).
Inkscape 0.92.1pre2, Linux Mint 18.1
Test case uncovered two bugs, both involving the handling of moveto/lineto records, which disable "fill". The included patch resolves the issue. Committed as revision 15525.