I would concur with a number of experienced posters on this thread having just completed a four storey town house with what looks like an identical carpet. Much as my stair extraction technique has improved I still undercharged big time for that job after all those treads and risers. Still, you live and learn.
To the OP: The pile on the carpet you didn't work on has been flattened through normal use. The bonneting of the DF machine has merely raised the pile on a number of the loops which, in all likelihood, have been lifted or pulled at some point in the carpet's life and would return to flat after a short period of normal use.
Re. Mr Callinan's posts, I can't see any criticism of DF anywhere by the OP. He came asking for advice, which he received, some of which was from DF themselves. If someone were to take the time and read the OP's posts you can see that he enjoys and has had considerable success in using the system.
Just a few thoughts.