In Modo importing CAD files that have been converted to a Polygon format such as LWO FBX or OBJ often contain a Vertex Normal Map. Exporting from Moi3d as LWO works well for example until you change anything on the imported mesh.

I got a nice tip today from @funk on the Modo slack group it basically replaces the Vertex Normal map with a Standard (as of 13) Hard edge workflow.

To convert open the Game Tab in Modo and click on the Convert to Hard Edges, set both options to true if you want to remove the existing Vertex map, which is the the whole point here so you do.

Next you need to Change the Smoothing setting in the Modo Material Properties to: clear Crease by Smoothing Angle and Set Weight by Polygon Area and Weight by Polygon Angle.

Pretty nice and quick way to set up hard edges for smoothing in Modo if the imported mesh already has vertex normals