LOL....yes, my current shep was a rock muncher as well when she was a pup...didn't make any sense to me at all. Big rocks, little rocks, in between sized rocks but never my socks or my 25 year old Scotch.
I do remember even finding smaller stones in her poop.
I recall just getting on her and using the old "leave it" or "no". Over a short period it worked and I probably used a high priority treat when she obeyed. I also remember using verbal distractions since I wasn't about to chase her and take them from her...I'm sure if I had, she would have just viewed grabbing rocks and munching on them as a precursor to a game of chase.
Pups love to chew and explore with their mouths/taste, so the sooner you get Titan accustomed to what is acceptable chew items, the sooner Titan will quit ruining his first set of teeth.
SuperG a la Dr. Seuss