[bch]

I thought preheated was the LEAST shocking to devices in the oven, otherwise they're in the cold oven (fine) until you start heating and they take the full energy from the elements trying to get the env to temp(not good). I guess too it would depend what the dishes are being set on in the oven - wire rack versus pizza stone/steel, ... I wouldn't think the hot air (poor conductor) would be as shocking as the direct energy from the full-on elements.

Unless your mac&cheese was premade, put into the fridge, then directly into the oven at cook time?