I've been looking everywhere I can find and I'm not sure I am correct about the Black Chocobo Chick. It looks like it may just be a minion as you said.

Yoshida stated that first the Player Housing would open > then the Stables would open > then you can raise your own chocobo.

Not sure the timing. Sounds like the Chicks will be rewarded to players before the Housing goes live. I was, in fact, assuming that the Chick would be related to chocobo raising!

The Dev post concerning the additional companions does seem valid though. I was really hoping for a black chocobo companion! Maybe that's is still possible even if the chick is a minion.