By no means am I an expert in this area, I only have some personal experience, but I would have to disagree with the presenter also. I can't imagine that any being is born with an inherent sense of how to communicate and interact when there are so many tiny little subtle and "cultural" behaviors that can really only be learned...
Not just that, but I think a lot of other emotional aspects of development can be affected as well-and I imagine that that in turn has an effect on social interactions. My brother's dog Tiffany and her sister Sugar were both taken early from mom (or so we were told) and they both exhibit "suckling" behaviors with blankets. When they are overly excited or appear anxious they run and grab their blankets and suck on them-it sounds kind of weird, but they are NOT biting, they are clearly sucking A behaviorist we saw said she thought it may be an attemp to calm herself (but then someone also told me it could be obsessive compulsive?). I found it interesting that both girls exhibited this behavior-not sure if it's related.
Tiffany is also DA and similar to Riggs in the sense that she shows NO (or very subtle to the human eye) signs before she "attacks". That's how her foster initially realized she was DA. She was "fine" around his other dogs initially, and then "out of nowhere" she was on top of the other dog for no apparent reason.