This sometimes happens with very fine grass varieties, or in semi-shaded areas where the grass blades grow very thin. If you leave the material on too long, then yes, many sprouts will be pulled up when the material is removed. The problem is easily solved, however, by lifting the material early on, before the blades thicken and become lodged in the fibers. Lifting is sometimes easier if you get a stick and drive a large finishing nail (headless) into the end of the stick. Bend the nail and use it to penetrate the fabric and lift the fabric straight up, freeing the blades of grass. After lifting, the material will settle down on top of the grass and be held up by it. You may have to do this a couple of times before the grass becomes mature enough not to penetrate further.