I call bull. At the very least, its something that was heard, repeated incorrectly, forwarded in part, then mis-interpreted.

• video card isn't used for printing
• CPU cores aren't used as "additional procecessor/makeshift video card" unless the program is running in software mode. One or the other, not both.
• If this is a newer processor it may have an on-board video processor good for app-games and movies.
• full professional level card is needed? NO. There are Civil3D users who are running gaming cards with file sizes that make most computers cry.

Basically, sounds like somebody is trying to get Navisworks/Design Review performance inside AutoCAD using one of the shaded visual styles and failing. Yeah, kick*** hardware will help some but will never take it all the way for anything other than a very, very, simple model. Run it in wireframe, its the optimum for AutoCAD applications and use one of the other two programs for the in-context(pretty) pictures.