Perhaps the piece missing is that, in SM, almost all kindergarten math (and a fair amount of first grade math) is done with manipulatives and practical math stories (word problems). The description of this particular CC implementation appears to be lacking sufficient concrete practice, prior to the paper and pencil pictorial work.
SM spends two years teaching number bonds, with the term and visual introduced in K, but mainly in conjunction with manipulatives. It's only in first, after plenty of opportunities for establishing number sense with concrete practice, that the symbolic representation of number bonds is used more in a paper and pencil context.
And yes, kindergarten is the developmental range when most children are just beginning to develop conservation, so even the manipulative play may be beyond them--though it may also help them to explore conservation.
