Guess I've never put a pile of dust on the floor or bench and watched to see if it eventually disappears with just the air cleaner on but I doubt it would. There just isn't enough air flow from a ceiling mounted air cleaner.
Does it move the dust already suspended in the air? It should because that is it's function - to move it into the air cleaner and catch the dust in the filters between the front and back of the cleaner.
Using the cyclone with one of the gates open is a great idea and I'm sure it moves the dust in the air but it also moves it quickly into the collector. The air exiting the filter should be as clean as it is possible, assuming the collector has a HEPA filter.
If I do work where it appears that more dust has escaped from the tool itself than usual, I usually run the air cleaner and the dust collector with the gate open for about 5 - 10 minutes and try to take a break while I'm doing it either with my dust mask on or out of the shop.
The fact is that there is always some dust that escapes, but I don't want a lot of dust piled on the floor or benchtops. That dust will eventually be disturbed by me and then it does get back into the air.
I just firmly believe in using all possible means of collection with the best filters available and, because there is some that escapes, I also protect my lungs with a mask of some sort.