This video shows what we at Chem-Dry of Tampa FL would call and extreme carpet cleaning. The carpet cleaner in the video is using a rotary extractor to tackle this extremely soiled carpet. They seem to be doing a great job of cleaning the carpet but it's difficult to tell because they did not groom the carpet before ending the video.
At Chem-Dry of Tampa, we use a rotary extractor on all of our carpet cleaning jobs, extreme, or otherwise. When using an extraction machine, like the one in the video, it's important to groom the carpet afterward so the swirl marks and cleaning patterns are gone. With the carpet groomed it's easier to tell if there is any soil still sitting on the carpet.
If you have your carpet professionally cleaned always ask to have the carpet groomed after the cleaning. It will ensure the carpet cleaner has seen any spots or soiled areas that were not fully cleaned. Even if your carpet cleaner doesn't use a rotary extractor and cleans with a more typical floor cleaning wand they should groom the carpet as the final step in the carpet cleaning process.