Not putting solid food into your system for long periods of time (months, years) will destroy your ability to digest solid food when you start refeeding. I've seen people in eating disorder facilities who have lived on diets of liquid food (historically Ensure, basically the same thing) who have not defecated for months, and when they start eating again suffer for weeks and weeks from horrendous constipation, often r…
Having entirely lived on Soylent for a full year and having went back to solid foods with no weaning period and no ill effects, I doubt the veracity of your unsubstantiated claims.
Unfortunately, we lack a corpus of evidence of long term liquid diet feedings (and intestinal investigations), mainly for ethical reasons, but there is at least one good rat study I could quickly recall: http://link.springer.com/article/10.1007/BF01308310 There are, however, countless great articles I suggest you read on liquid diets and their impact on satiety and other important illness recovery markers. One of the important topics for researchers has been how to safely transition patients more quickly to solid food, given some of the less desirable side effects of the liquid food diet.
And yes, I understand that the Soylent team is confident that they've solved, for example, all gastric emptying issues by adding exogenous fibres. I'm positing that for every variable they're convinced they've figured out, they're opening up another potential set of problems that they've not even considered. Their latest opacity on this recall isn't giving me hope that I'm wrong here.