Wow... just wow.... totally right about the much earlier reference... kudos!
But, I don't think that we would necessarily have been forewarned of unexpected factors -eg the return of Z'dtrri came out of the blue. That's the point of things happening off-screen- Rule of Drama, when they are revealed in the right moment...
Just saying that the Giant so far has not introduced a character without exploring his/her full (roleplaying) potential, and Malack has not yet shown his. From a pure metagaming prespective, it could just be his time to shine.
But maybe I'm just being paranoid here...