scale of exported dxf not the same after import and open of pdf via poppler

[Sjoerd]

I have a pdf and I created a dxf in two ways:
1) File->Open and tick "import using popppler", then export using File->Save a copy or File->Save as and choose Desktop Cutting Plotter
2) File->New and then File->Import and tick "import using poppler", then export using File->Save a copy or File->Save as and choose Desktop Cutting Plotter

The dxf in case 1) is about 80% as large as that in option 2).
After importing the the sizes of objects on the page are identical, both in pixels and in mm. However, after exporting to dxf and back importing you can see that they were exported at different sizes. (as if inkscape read a dpi from the pdf and corrected for that somehow during export. however, in that case I would expect to find this scale factor in the document settings somewhere.) It is not a dxf import error since the size difference are really in the dxf as can be verified with any dxf viewer such as librecad.

The problem does not exist when not using poppler. to make things worse, it seems to depend on the pdf as well. I have attached one malfunctioning pdf.