thats not how that works. stone and steel are both exactly as conductive at one temperature as they are at another, at steady state.

i dont mean to say the conductivity changes, but the thermal conductivity of steel is too high that when its hot enough it will have too much stored heat and will burn your pizza. stone, having a lower conductivity will release its heat more slowly

also, conductivity is determined by (at least) material, shape, and temperature