I don't think that 'The nutritional value of a food is based on it's composition.' is too wild a claim.
I have almost no knowledge in nutrition.
But I know we absorb things differently depending on what we found them in. We absorb protein differently if they come from mat or from vegetables. We absorb calcium differently if it comes from milk or from a pill.
So in that case, I think think that assuming the nutritional value of some food comes only from its composition is a claim that needs serious backing.
The makers of Soylent, on the other hand, are pretty good at making broad sweeping nutritional claims without bothering to back them up with legitimate science.