Errr, I don't know about that hitbox but don't forget the other hitboxes. Brand Q is legit dumb as hell. Not to mention Blitzcrank/Thresh with their hook hitboxes out of bounds. We all know hitboxes are larger at the end of the hook, it's just how it is. Same goes for Pyke.
Is Pyke balanced? Meh, he has low health for most of the game (he can literally get blown to pieces of you CC him with anything, as he will be stuck and has like 1800-2000 hp in late which means a 3-4 hit for most adc's. Sure he's dangerous and he's obnoxious in lane but once he's in teamfights or gets caught he's done for. His invis gives you an animation around yourself and it's not true stealth so being close to him = you seeing him. In my opinion I hate lanes like morgana/blitz more than pyke, because Morg Q has some r%%%%%ed hitbox that just flies around every 8s and locks you down for a good 2-3s. There's bigger issues in this game than Pyke's hook.