Could you? Yes.

Should you? No.

I mean you can cook on an cars engine exhaust (tho good luck finding a place now they the engine bay is just plastic covers) or cook a fish in a dishwasher (wrapped in tin foil)

I do the opposite use a cheap dehydrator to dehydrate my filament. I don’t own a filament dryer, because I bought the dehydrator before commercial filament dryers existed, so I can’t comment on the inverse.

theoretically? yes.

several problems.

Food dehydrators typically apply heat as well, and sometimes significantly higher than a filament dryer.

Then there’s the cleaning and bacterial contamiation issues- food dehydrators are made to be easily cleaned so as to prevent bacteria doing nasty things to you.

Then there’s the various resins and solvents that sometimes off gas becoming toxic.

Microplastics is far down the list if you’re desperate, but it’s there too.

but otherwise, they’re still basically the same device A heater (maybe) pushing warm(ish) air over something.

I would fear the bacterias. Bacterias love temperatures between 40°C and 50°C. I don’t know about the typical temperatures of Food Dehydrators. But filament dehydrators are targeting these temperatures.