Yes, they know about the b12. But there is some variation, when people don't supplement, in how long it takes for a frank deficiency to develop.

I don't think I'm speculating about individual variation there. Variation is a given. People vary, there will be variation in how quickly a person develops a particular deficiency if they are deprived of a nutrient. It would be kind of weird if this wasn't true.

On the cocoa--stearic acid thing, just how high do you think the daily requirement for dietary stearic acid is, anyways? I didn't even think there was one. It's not considered an essential fatty acid, that I know of. Not that I don't think eating it's a good idea, but on what basis is it essential?