Because the implication is a random human-generated recipe from wherever has any more risk than the one generated. People who would trust a 'bleach recipe' from AI would also trust it from a Tiktok video or whatever.

Edit: it is irrational to think this way when someone prepares your food¿

But that's just a made up implication to make the other one look better, that's not the only true alternative, so doesn't explain irrationality