If you say “heat conduction”, what experience does that lead you to anticipate? Under normal circumstances, it leads you to anticipate that, if you put your hand on the side of the plate near the radiator, that side will feel warmer than the opposite side.
Metals conduct heat much faster than air, so if conduction was the only mechanism responsible you’d expect both sides of the plate to be at nearly the same temperature.
A1987dM comments on Fake Explanations