Don't words like kiatu contradict the following statement in the tips & notes: "All of the nouns will either start with ki- in the singular or vi- in the plural, unless the stem begins with a vowel. In that case, the concords will be ch- and vy-."?
Might be worth pointing this out to BrandenRyan on his activity feed. It should probably read "most". As is generally true of many rules, there are exceptions.