They programmed Atheon and the templar to move away from zones that cause damage like the ones from your grenades and supers, and they forgot to put up invisible walls to stop them or they didn't foresee that people would push them off. That one is on bungie. As for crota, the fire team leader is the connection host, so when they leave it automatically finds the person with the best connection and it just so happens that crota gets stuck in a knee position. And you could argue that it's a glitch so you are not modifying the connection or your device. And as for sony's agreement they can't prove you did it on purpose unless if they specifically listened and recorded you saying "hey let's cheese crota by messing with the connection" of course you can say it differently.