True.Your chickens are not fed a vegan diet only their feed is vegan. Mealworms and any bugs they find free-ranging negate them being fed a vegan diet. They would be considered to have an Omnivore diet based off of your own description of what you feed. To be considered truly Vegan or even Vegetarian bugs also can not be eaten. Omnivore means eating plant based matter as well as any meat and insects are included in this. In fact many insects are classified as omnivores because they eat both plants and other insects. Some insects are even classified as carnivores because they solely eat other insects.
I was only saying chickens in factory farming get a (100%) vegan diet.