The unique affix turns the Chakram skill into a Hatred generator: instead of spending Hatred, it generates it. For all purposes, it will count as a Hatred generator afterwards, but will not become a Primary skill.
Despite the Game Guide stating it has 3 random affixes, it actually has 4, to the total of 7 (like any other legendary Quiver).
Stats (Level 29)
Spines of Seething Hatred
Seeing their enemies flayed serves only to fuel the thirst for revenge that burns within a demon hunter’s breast.