He's dead wrong. I've had mine a while, and know other people with the case that have had it for a long time now... no issues. He would be the ONLY person i've heard of with a cracked incase slider, ever.
That said, i'd have to say he probably did something to mess it up....
he did i think, used too much pressure or something but he was just complaining about it, he did say the bottom part has slid off unknown to him...