This is because Soylent is making up for deficiencies in its ingredients. They need to add Vitamin D, calcium, and vitamin a palmitate, for instance, because there is no Vitamin A or D or calcium in the canola oil and sunflower oil. These nutrients are already abundantly present in Skyr and cream.

I wonder if the bioavailability is even good in Soylent. I know some of these nutrients are much more bioavailable in animal sources than plant sources (though I can't recall which), so the vegan-friendly label on Soylent is a mark against it, if health is your goal.