Not exactly.
He wasn't making the food himself, but he was providing an ingredient that others used in their own recipes. He also distributes the recipe along with each batch of his ready-made ingredient, but the de-facto method of using this ingredient is to just use the ready-made one, rather than making it yourself from his recipe.
Many people just use the latest batch of his ingredient in their recipe, without checking the recipe for that batch to see if he decided to slip in something nefarious.
The analogy here would be that while he didn't mind the small home industries using his ingredient for free, he didn't like that some big corporate bakeries were using it without supporting his recipe development.
He could have just decided to stop improving his ingredient any more, and everyone would just have to make do with the latest batch.
Or he could have withdrawn all of his batches of ingredient, and forced everyone to find someone else to make the ingredient for them.
He chose to poison the new batch.
Ironically, the majority of big corporate bakeries using his ingredient have already settled on a particular batch, and although they might try out the new batch internally, they won't use it cakes that they sell to customers until its been thoroughly tested in-house, and since they noticed that their taste-testers keep dying when using this batch of the ingredient, they just know not to use it in anything they sell to the public.
But the small home industries that he actually wanted to benefit from his ingredient often don't have the experience to vet each batch and taste the dough themselves since THEIR recipe hadn't changed, so they just use the newest batch for each cake they make, and end up poisoning their customers instead.