Hi!
Let me explain a bit what is going on under the hood. It won’t solve your problem (yet) but that will remove some guesswork on your end.
Rhino stores data in different “buckets”. The Nurbs curves and the Render Mesh. When you pick a render view in Rhino, the Rhino viewport is replaced with the Render Mesh. In wireframe views, the viewport displays the Nurbs curves.
When we read 3dm files, we are reading nurbs data and generate static meshes using our own tesselator. At this point we are completely blind on UV information and the result appears like “data loss”.
For 4.25 we are working to give you the option as to what “bucket” you want to import → Nurbs or Render Mesh. When we read the render meshes, we will have the Uvs and be able to display them correctly. The downside is that the mesh resolution will be baked by Rhino and you’ll need to define that prior to import the data.
Hope this helps,