People were buried in the dirt for many many years all over the world.
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You’re right. I can’t speak to what humans did with their dead through the millennia, but I’d be surprised to learn their families tried to grow food on top of the bodies. Death is a stinky and messy business, so the dead have always had their special resting areas away from where day to day life happened, even without the formalities of caskets and cemeteries. I imagine the laws that say we can’t just bury Mom in the back yard also have some sound basis in hygiene and medicine. Composting humans and using them for fertilizer, potentially within months of death, doesn’t seem healthy or wise. YMMV
She said she didn’t care what they did with her compost. Maybe fertilize trees for instance.