Bambara has apparently been a staple in Western Africa for centuries. So if it had any critical nutritional deficiencies I'd imagine a cultural/culinary solution would have presented itself by now. And the B12 in Bambara is uniquely bioavailable; unlike the b12 in most other plants.

Rentinol (vitamin a) is not an amino acid. It is a fat soluble molecule which is why you get more from fatty sources. It's a logical train of thought but you're comparing apples to oranges.