How can you generalize all the nutrient and calorie requirements between two people when people have so many different body sizes?
The RDAs are a general rule of thumb. People who need more calories or less calories know it and they make those adjustments on their own. Soylent is 2000 calories a day. What other measurement would you have them use to make Soylent other than the RDAs?
RDA for micronutrients such as vitamins, amino acids, etc. don’t really change with different body types (with a handful of exceptions). As for macronutrients, what really matters is the ratios. If you have a good ratio - which Soylent does - all you need to do is take in more or less calories and they take of themselves.