I was very surprised reading this because my school's textbook claimed that microwaves heat food using the resonant frequencies of water. This fact was drilled into our heads over the course of multiple tests. It's disappointing that millions of students every year still learn this incorrect explanation.
And yet any of us could've very easily disproven this and it doesn't correspond to our experienced reality and yet we all believed it because we had be taught it in school.
I wonder if false teachings like this can create a mistrust in science from an early age?
We also need a list of things that many people believe are true, but have no scientific basis. I.e., things that may be true or false, but no study has shown conclusive evidence either way. The medical and personal health fields are overflowing with things that people believe for which there is no evidence.
As a heavy coffee drinker I’ve learned I reduced my cancer risk and increased it, back and forth for years according to trending studies.
Ah, like most of history...
"We are sorry for the inconvenience, but we currently lack objective sensors to send back in time and gather data for an evidence-based approach. We regret to inform you that our history department will be closing after critical objectivity is reached on our campus, anticipated in September of..."
...never. Subjectivity is a natural law, it's universal to the experience of the life form. Objectivity in science is a code name for "measurements that facilitate social bond-building" and while this has its place, the other subjective, theory-generating, guessing-supposing-believing half of our reality cannot be repressed if the results are to be qualitatively "good." We need to become comfortable with, or simply continue to develop as best we can, the deeply organic and chaotic question of quality if we are to evolve beyond current objective limitations. Until then, even "hard science" when pushed to drive out all subjectivity will continue to be filled with scandal, the dark appearance of the subjective realm. The best we know of good must be taught or the repressed spectre will spring us right back to the worst kind of jihad, it will continue to give us the physicists who joined Aum, etc.
I think the main reason this myth persists is stuffed/filled food items such as pizza rolls, burritos, Pop Tarts, Hot Pockets, etc.. With these, there's typically an outer layer that is thermally insulating and lower-density, while the filling is more thermally conductive and higher-density (water/fat). This means that even if the temperature is uniform, the filling will be perceived as much hotter than the outer layer.
In that vein, it's not really wrong to say that the food is cooked from the inside out, so long as you don't understand to mean that it is literally cooked from the exact middle. The heating is still coming from the interior which is conducting heat to the exterior shell; that's it the outermost layers of the interior filling that's heating, not the innermost layers, is a minor detail by comparison.
I routinely use a microwave to pre-heat the inside  of something before finishing it off in an oven or toaster oven (sometimes in convection mode). That way, I gain the vast majority of the benefit of speed from my high-powered microwave along with the mouthfeel and caramelization benefit of the traditional oven.
The contrast can be particularly stark (and useful) when working at temperatures above boiling.
I once ended up convincing my Mom into using the "cooking the inside" heuristic of a microwave in order to save an apple Charlotte that came out with uncooked dough in the center . It took a few single-minute zaps to get it there, but it worked great.
 Well, of course, the whole, but it's the inside that's important for this exercise
 She was quite distraught because she'd never had that failure in the dozen-plus times she'd made the cake previously. Despite being a veteran of the semiconductor industry, she suspected herself first instead of the oven hardware, which it turned out to be.
Infants can and do feel pain.
.... not that I've done that.
...and it's terrible security and it's still prevalent installation method of downloading random binaries off of the internet and then executing them with administrator permissions.