If you even just barely touch the dark areas, you will see a lighter looking "smudge". However, it's been my experience that after the canvas has been finished with an acrylic gicleƩ coating, the marks disappear. If you can manage, guide the print to feed on the outside of the cloth "catcher" and cut it off the roll end when finished...without the print feeding into the basket. The rough texture of the cloth sometimes leaves marks when the print feeds into the "catcher".
I've also seen scratches from the "catcher" on film where the ink doesn't dry very quickly.
Another tip: In our studio we've noticed that some canvas coating liquids applied with a roller will "Pull" the ink off slightly unless the print is allowed to dry overnight.