The problem is the misuse of the word “vegan”. Veganism is a moral philosophy. It is more like feminism than like vegetarianism. Veganism has to do with animal rights and liberation. That has consequences on the diet a person eats but also all other things a person does and doesn’t do. None of these studies are concerned with or discuss the rights or experiences of animals, so they aren’t about veganism. It’s a relatively small thing except that veganism is so poorly understood, so extra diligence is always appreciated.