Not sure what website you visited but the very first entry that popped up in a google search produced the site which this quote comes from:
"Most animals and plants are unable to produce vitamin B12 directly. The vitamin is produced naturally by bacteria, and it is also produced as a byproduct of activated charcoal production (in the form of cyanocobalamin). Many animals have bacteria in their digestive systems that produce B12, and some algae, such as chlorella, receive B12 from a symbiotic relationship with bacteria. However, humans generally do not have these bacteria and therefore need to consume it from other sources.
The scientific name for vitamin B12 is cobalamin, which is produced by bacteria. There are several forms of the vitamin, including hydroxocobalamin, methylcobalamin and cyanocobalamin, the latter of which is often used as a supplement."
I have had excellent results with both algae and chlorella so while Im not typing that its necessarily right for you personally, its also not so difficult to address a deficiency of B-12 in the vegan diet.