I think it would, Hopkirk. Imagine if the water level when cold was set to a fraction below the overflow level then, when it was heated it would cause an overflow to get rid of the expanded volume of the entire heated water in the system. Upon cooling, the entire water in the system would then contract and drop the ballcock below it's normal full level and thus automatically refill up to the overflow pipe again.
I think it all depends upon where the water level is when cold and therefore, the ballcock arm could need adjusting to lower the water level.
And then again, my friend, it could be something else completely different and too technical for us non-plumbers.