So it’s made of shit, right? And shit is an animal product. But barring a night of drinking or a particularly aggressive burrito, shitting does not harm the shitter; it’s beneficial and required. Also the animals in question can and do consent, does that make it vegan?
…Maybe? Usually, people are referring to nutritional things animals produce for themselves or their offspring, like milk, eggs, or honey. But shit is just the byproduct, not a product. It’s what’s leftover when your body is done extracting nutrition. Like, if a vegan was composting, they wouldn’t refuse to put dog shit in it, would they?