Protein shakes and meal replacements almost always show the amount of protein/fat/carbs. Usually they reserve these "secretive" proprietary blends for creatine, NO3, caffeine, and similar muscle-building or preworkout supplements. I see what you're getting at it, and I agree they might not have to list it, I just think it would be nice to know and perhaps would increase trust.
I'm in the same camp as the author, saying that people overestimate the harm of fat. I don't think I need 56 grams of fat in a serving of soylent, though. Let's assume I want to maintain my bodyweight and need about 2500-3000 calories to do so given the amount I exercise. Two servings of soylent will give me 1600 calories from carbs, 400 calories from protein, and 1008 calories from fat. Maybe that's fine, but maybe it's not ideal. I guess I'd like to know. I think it's a stretch to say I have no clue what I need. Maybe I don't know what I need to survive, in terms of a bare minimum, but I know what I need to maintain my weight in terms of calories.