ive been looking this up on the net for about half an hour. Apparently that bit with the guy barricading the door happens EVERY single time no matter what you do, which leads people to believe it is in fact scripted. However, it is also being said that valve never said that that particular scene wasnt scipted, just that most of their AI was non-scripted. But pretty much for the rest of the demo the AI 'seemed' to be non-scripted.
Im sure they would have liked people to believe that such a great shot of an enemy barricading a door was non-scripted, however whether or not they actually claimed this is another story. Im not too sure as there were no clear-cut articles about this. just thousands and thousands of forums...
Anyway im not even too sure it matters. its gonna be a great game with lots of parts involving non-scripted AI which will be very cool. They wouldnt be able to say that unless it was true cause people would find out WAY too easy after the release