Yes stuart you are correct it will greatly affect the airflow, this was the practice some29 years ago when steamvac used a weighted floor tool which nearly broke your back when trying to get it into the customers house, I personally think that extractor products are lost in a time warp somewhere in the late Seventies early Eighties?
I am glad I went down the truck mount road, I have a titanium wand with a Teflon glide which even considering the enormous airflow/vacuum created by the maxx450 diesel it simply glide over the carpet no need for weights, I really think people like extractor should know better, as they have been trading slightly longer than myself.
All the best Ted