The model's hatch window is translucent in-game, but only enough for movement of the steam and fire effect from the Fire Salts to be vaguely discernable through it. It's dark enough inside that no one could identify whether or not there's food. It's easy to just delete the AlphaProperty node in NifSkope to get rid of that, though. I could make it so it could be opened, I think...probably. I've never worked with making hinge animations. Certainly not during the busy season with my job, unfortunately...and even then, Oblivion's collision is too wonky to put food on the grate inside without weird bouncing.