He still drank a shake, and at no point does he claim to have reformulated the mix by adding to it, or deliberately attempting to chemically alter it, or switch to different products.
Anyway, human nutrition must be capable of tolerating human error and envionmental hazards. It's not like this is some kind of a high-powered pharmaceutical. If anything, there should be room for that kind of error, because an inability to tolerate mistakes would actually be worse when it comes to food. You really don't want a casual fumble to cascade into some unforgivable and horrific, punishing mistake. You want to have some flexibility for spills, or maybe drinking an extra shake here and there, if you skipped dinner and breakfast one friday night/saturday morning.
If this behavior actually did introduce augmented outcomes, then consider this an important caveat of the product. This means it's sensitive to specific mixing habits, and is prone to user error. This would be an important detail to shake out during trials.
If the powder settles oddly during shipping, or mixes unevenly, and demands thorough mechanized blending, those are important instructions to communicate explicitly. Otherwise, if a bag lasts two weeks, and all the fine particles of vitamin powder settles at the bottom, leaving the fiber at the top, and you don't mix and shake the bag, it might take you a week to reach the bottom of the bag, and you'll inadvertantly be overdosing yourself with fiber one week and vitamins the next, when you try to finish off the bag.
I'm just speculating, but when consuming Soylent I would assume that one needs to eat all of it (or rather, all of the dose, if that's the right term).
My only beef with the paragraph was that he's reviewing a food source, the first review by a non-member of the team. If he'd done this for a publication, you can be sure his editor would be chewing him out for such an action.
Real life consumption, sure, I've spilled plenty of dollars worth of protein powder. I, also, wasn't the first one reviewing it and/or testing its claims.
"...The white stuff that was mixed into the tan stuff was floating to the top and congealing together... So I just started just scooping them out... I’m pretty sure the white chunks were the rice protein, and perhaps something else important."
You're the first review of Soylent, and you throwing away blobs because ...? It looked icky? This is a meal replacement focused on giving you exactly what your body needs, and it just seems like a terrible move to throw 'what your body needs' away.