I'm probably wrong about this, but A) the use for the GS Ball hasn't been implemented yet, and B) I think it was because he had some troubles implementing another HM, or he was just too lazy.
Alternatively, you can check the official info thread:
http://www.pokecommunity.com/showthread.php?t=100537
Off-topic, I somehow just found a new Fire Emblem hack on that board, and I do believe I happen to recognize the name of the guy working on it.