The makers of heat 'n eats are beginning to abandon "conventional oven" and make their products microwave only. I now read the fine (frosted) print before I buy a heat 'n eat after I brought home a couple that demanded microwave only. I don't have a microwave, mostly 'cause I lack the counter space for one, so a microwave only heat 'n eat is useless to me.
Then there was the one that ordered me to remove the food from the plastic tray, put it on an oven proof plate of my own for cooking. Which totally destroys one great benefit of heat 'n eats, no dishwashing after dinner. I suppose the maker had been messing the the composition of the plastic tray and feared that his new concoction would not take the heat of the oven. Way back, before microwaves, heat 'n eats came in aluminum trays. After the microwaves came in, they shifted over to plastic trays to avoid blowing up the microwaves.