That clip helps hold the screen down on the top. I am sure that apple would not waste the time or money to install millions of them if they did not do a better job with it, than without. I own a repair shop and if I remove anything from a phone it gets put back in the phone. I do this everyday and I do not pretend to know more about these devices than the manufacturer does. I do not want a reputation for leaving out things in a device. Sure way to ruin a reputation real quick.