The Humanoid trait Knowledge Focus (p21) costs 2 points, is a class-only trait, and increases the maximum traits by 1.
Is this just the most useless trait ever (since you buy a trait, taking up a trait slot, to increase the max traits by 1); did I misunderstand something cool about this; is the class-only a typo, and should it be species-only; or is there something else going on here?
You are looking in the old file xD in the errata the trait was rewritten to 'species trait only'
Read the Ability description on page 168. [Maximum Class Traits X] does not count toward the allowed number of Traits for a class. It is effectively the Bonus Trait Class Option with a 2pt cost.