All purpose flour is fortified, doesn’t make it a supplement. Did you even read your own source. It literally says that nutritionally yeast can be unfortified and it have b12
> "Yeast cannot produce B12, which is naturally produced only by some bacteria.[8] Some brands of nutritional yeast, though not all, are fortified with vitamin B12. When it is fortified, the vitamin B12 (commonly cyanocobalamin) is produced separately and then added to the yeast."
Furthermore, fortified all purpose flour is not the same as fortified nutritional yeast. In fact, what you are referring to is likely _enriched_ all purpose flour. This has vitamin B1, B2, B3, B9 and iron added to it. There is no addition of vitamin B12.
https://en.wikipedia.org/wiki/Nutritional_yeast#Nutrition