Oh, I realize that B12 is an essential supplement for vegans, and even for many non-vegans. The thing is that I don't think that vegans need to supplement any of the other B vitamins, and from what I can tell comparing labels of fortified and non-fortified nutritional yeast, it seems that they do add other B vitamins besides B12 (random fortified label on the left and random non-fortified label on the right, comparing similar quantities of yeast):

Some B vitamins should not be consumed in excessive quantities (mainly B3 and B6, with B9 also having some negative effects). I realize that it might take a larger amount of fortified nutritional yeast than one is likely to consume to exceed the upper limits, but personally, I would rather just avoid it altogether if I don't need it. I avoid B-complex vitamin supplements for the same reason, as those very often have massive amounts of all the B vitamins.

There have also been studies linking excessive vitamins B6 and B12 intake with significantly increased risk for lung cancer, especially men and particularly smokers*:
https://examine.com/faq/do-b-vitamins-increase-the-risk-of-getting-cancer/
https://pmc.ncbi.nlm.nih.gov/articles/PMC8012225/
https://pmc.ncbi.nlm.nih.gov/articles/PMC6642017/

In conclusion, I personally prefer to take a normal, fixed amount of B12 supplement per day, and get my other B vitamins from natural sources.

* For others reading this, please don't take this as a reason to avoid these vitamins, as having too little of them is also bad for you. Moderation is the message here.