Starting with the latter first, the lack of properties in Blender is expected behaviour; we aren’t transmitting properties between applications in almost all cases. I have flagged it in our systems as a feature request.
Regarding the 3D solids with properties, I can see that you are right in your observation, but I don’t have sight of the original model, so I don’t know if there is an issue to rectify. If possible, please share something with us - it can be a minimal set of information in Civil3D.