Dictionaries are just someone's attempt to record how people use words. They're not authorities on meaning, just records of use.

If someone says they're vegan you would expect them to use no animal products, including clothing, nail polish, colour pigments etc. That's not controversial, you can find shampoo and jackets marked as vegan it is a common understanding. That is just incoherent with health motivations, and indeed many "vegan for health " people do use animal products and have cheat days and crap. They aren't vegan, they're just dieting.

People call themselves lots of crap, doesn't make it true.