While I did not find a definitive answer as to why SketchUp imported this DXF of lines as faces instead, I suspect it ‘might’ be the SVG to DXF converter. I found a tip in at post in the Import SVG image and extrude based on contours - #8 by AjMwd article that provided the solution.
I ended up downloading/installing Inkscape (Inkscape.org) for the SVG to DXF conversion, which worked great AND came into SketchUp as just lines. My Inkscape procedure was…
- Open SVG in Inkscape.
- Save As > Desktop Cutting Plotter (AutoCAD DXF R14) *.dxf.
- Options: use LWPOLYLINE type of output with a Base Unit of “Inch”.
- All other default settings.
The contours came into SketchUp (Pro) just as lines, quick and easy. It appears that was not a SketchUp issue but rather an issue with two separate online based SVG to DXF converters? Though that is not confirmed.