Old issue, but annoying nonetheless. Less of a problem when outputting STL files (for printing) which only support polylines and not arcs/circles. Funnily enough, 3D printers nowadays support arcs natively in G-code, so some slicers support detecting rounded polylines and converting them back into circles or arcs.

Found a script[0] that does this for DXFs in a github issue[1].

[0]: https://github.com/nophead/Mendel90/blob/master/dxf.py [1]: https://github.com/openscad/openscad/issues/4605