RE: Let's talk thread lock (and shimming)
You're right. Metal does not contract when heated. It expands. For this reason you always adjust the valves on a 4-stroke (with solid lifters) with the engine cold as the tolerances tighten when the parts are hot. Differing temperatures will give differing tolerances.
Now, I doubt a hardened clutchbell will expand much, but I surely wouldn't leave any more play than what is necessary. There's always more than one way to skin a cat though.