The purpose of removing beads in this particular way is to strengthen the first three fingers. This first photo is what we call a tripod grasp (index, second, & thumb). The second photo is what we call a pincer grasp (index and thumb).
During this particular activity we want to use these three fingers only to remove the beads, looking out for fingers to be in these two particular positions. It is okay for them to bring out one or two more fingers to help stabilze and manipulate putty, however not for the entire time.