” there’s straight up Halacha that says burnt substances of any food are no longer considered food”
this is what I consider dangerous talk. Yes, maybe a ‘straight up Halacha’ says that, but we have no reason to believe an oven that is warming things gets hot enough to burn substances to that point. And what if they are in together? And what about the 10 times you use the oven while it is not yet burnt (if it burns at all?) When you throw out a known halacha as an aside in a conversation, even though it does not actually apply here, people get sucked in. And you can be misleading a lot of people. It is not being a machmir, it is about not making assumptions about anything that isn’t assumable and calling it a chazaka.