This is silly and trivial. Two reasons:

[1] The phrase is the analog of an idiom. It is shorthand for "hierarchy" and used as such. The parent is explaining its use.

[2] There are many tribal organizations. This cuts both ways. Provided there is a single one that was historically rank-hierachical, the data is not even a counterfactual.

[3] Provided [2] is ok, so is [1]. We know [2] is ok. Hence, the comment is logically ~gratuitous.

See, for example:

http://www.usingenglish.com/reference/idioms/too+many+chiefs...