It is my understanding that the streaking is a straight line rather than swirls.
Another thing to enter into the equation is that the newer 360i Quad has higher vac shoes, the exact same as the Rotovac XL, so they bring the jets to a higher level off the carpet.
I have found that the swirl marks are generally able to be groomed out. My twin head Rotovac at times was a bear to remove swirls, as I would often go back over the carpet with a wand to help.
I think the straight line streaking that is possible comes from higher heat and slower movement of the RV over the carpet. It may be like my old SteamWay wand, where on some carpets with the close to the fiber single high flow jet and very high heat would do the same thing. Almost like a distortion rather than a clean streak.
I am not 100 percent sure what has caused a slight straight streak a time or two, but if I adjust to it, it seems to be avoidable. Cleaning pattern, speed, heat, adjustment.
I love my 360i quad. Not too heavy to ever not bring in and use and so much easier than the twin head to use. I now even use it on stairs.