My point is that the heat increase of the heart doesn’t have to be so insane. If someone was designing a microwave human heater they would have to make the power level such that it would always result in a safe rate of temperature increase. Obviously using an off the shelf food microwave wouldn’t work.
Is heating someone too quickly a concern if they don’t have hypothermia? Like if I’m sitting round in my house and start to feel cold, and I get in a hot bath, it’s not going to heat me up too fast, right?