You do have to mow the lawn more frequent if you don't bag it.
I think most simple way to see how it work by trying. Adjust the mower high to middle, run the grass over without bag. You would see.
It wouldn't work for somebody like to cut grass very short and wait long time to cut. But If you are the person mower your lawn every week or two. then it works. It also reduce the weed in the lawn because you cut the weed before it could seeds, repeat it few time most weed would die.