Food has complex organic molecules in different arrangements and different densities. Not just the physical material of the substances but the molecules that make flavour. Like the difference between today's artificial food flavourings and real fruit's flavour molecules.
I imagine it's hard to get the balance exactly right. Maybe chocolate mousse is a little too firm, or soup is a little too runny, who knows exactly what it is about the "taste" of replicated food that makes it different from traditionally prepared and cooked food.
With a substance that is most likely just a copy/paste/area-fill pattern it's probably a lot easier.