Yeah sure. Maybe you could make the argument that humans should leave stuff like that for other scavengers who need the nutrients to survive, and instead opt for plant foods. But at those edge scenarios you would then also have to take into account the impact that plant agriculture has on wildlife. It's quite possible that scavenging and gathering is the most vegan option, but seeing how it's neither viable for a lot of people nor something that often comes up in daily life, it's easier to just generalize vegan food as plant based.