The main point of the video is - if you want to work with Solids in AutoCAD effectively, you should correctly set the DELOBJ system variable. What does this variable mean?
From Autodesk online help:
As Revit users, if we ever use AutoCAD for 3D modeling, we want to try and create a form that is a true 'solid', something that Revit can understand properly (as opposed to messy meshes).
It seems that this workflow is becoming easier. Of course, Revit itself is becoming a more powerful 3D modeling tool. Check out my post on Bending the Rules with Adaptive Points.