So it does not cover the whole spectrum and leaves out trace amino acids. Which is okay I guess, because they are trace. You would probs get enough of them from anything else you eat but I would assume that even if it is a source of "complete protein," you would not meet all of you protein needs if you ate soy or the like by itself.
But that is just an academic observation. In practicality it is complete enough.
Yeah, its one that most vegans echo (that's why I used the word "considered," since the FDA/USDA is usually cool with it and we were discussing the food pyramid). Like you pointed out, though, it doesn't go much further than an academic observation because most people don't susbsist solely on soybeans, etc.
The biggest issues in nutrition usually come with veganism. Since you remove the B12 from eggs and dairy, which is a concern. The only way to reduce this issue is through nutritional yeast or food rich supplements.
Raw vegans like to think that you'd get adequate B12 from the bacteria on uncooked foods, but yeah
that's not really the case.
I actually like using nutritional yeast in food, though. It has some interesting applications.
Also, flax seed oil can be used to replace cod liver oil, if you're a foodie jerk ! !