The experimentation that the Soylent folks are doing themselves looks like the fairly uncontrolled do-it-yourself kind, not like a real scientific study. It seems like it would be difficult to do properly because the formula of Soylent changes quite often.
here is the recipe: https://diy.soylent.com/recipes/keto-chow-104-master-rich-ch...
Its true that its hard not to sound like an evangelist when you've lost weight-- but it's not pseudo science when there are studies that support the hypothesis (of course a lot of diets are fad diets and are pseudo science). The thing is its hard to tell the pseudo science from the real science.
Personally, in my experiment, I'm going to try adding Keto Chow to my diet over the next couple of months and see how I feel about it.
While I think the term 'pseudoscience' gets thrown around way too loosely these days, it's no secret that the science surrounding nutrition is a convoluted mess, with various peer reviewed studies showing seemingly conflicting results.
And also with so many eating exclusively the soylent mixture which is easy to control what goes into, they got an excellent opportunity to study many hypothesis about food. E.g. how important is it to eat "live fresh food" vs just getting the micro nutrients in the right mix.