As noted, it is possible the CAD app is setting the lengths and angles of each of the vertex normals to specific directions and lengths, to suit its own preferences for how to shade a polygonal model. Removing those values in 3ds Max is a good idea if you’re going to be editing the vertices before baking, since Max won’t…
Also you can always export a hi poly model and transfer/ borrow normal directions from it. I do so with model copy dynameshed in Zbrush to tiny polygons. Max doesn't have a native tool for normals transfer but there are 3d party scripts starting with normal theft . Or you can always do it with data transfer in Blender…