This discussion has been about VEGANS, not VEGETARIANS. There’s a big difference. VEGANS eat no animal-derived products. VEGETARIANS eat a variety of animal-derived products such as milk and eggs, and often shellfish, and even fish. All of the latter contain B-12. Plants contain NO B-12.
As I learned dating young females in Southern California, vegetarians often eat fast food hamburgers, and fish, chicken, and all kinds of animals, since many of them are totally confused about what a vegetarian is.
Thanks for your clear answer.