No disrespect intended, but you are out of your depth and seemingly don’t realize it. You should not be nearly this confident. Instead of googling, “vegans need b12”, you should have googled: “cows b12 injection” and come up with some of these hits:
While this 20 seconds of research does not establish that supplementing B12 is actually necessary for livestock, it does go towards establishing that it is an industry-wide practice.