Yes, but they didn't cheat. They didn't show you Glenn die only for him to come back to life in another episode. What they did was do everything in their power to make you think Glenn is dying, but they purposefully shot it in a way that it could easily Nicolas that is being ripped apart. Whether you think it is bad writing, or you think its impossible Glenn will be able to survive, or you are mad at the camera angle, all of that is fine, but they still didn't cheat. There is room within the information given on screen that could allow for his survival, despite how much you have to suspend your disbelief. But this is a show where zombies are heard from a mile away in one scene and then sneak up like ninjas the next so that the writers can get what they want.