It is mostly about the glove, and they want him to dominate for more than 3 weeks. My guess is mid-May, 1/4 of the season. Complicating things would be Ehire. They may give him a little run once he's healthy, sending Luscious back down and sitting Alcides on the bench.
Im still not sure why he can't just stay down there until after the deadline. Again, we arent competing for anything. The goal of this season is to maximize value at the deadline. For that, your assets need time to produce.
I also think almost 400 PAs of struggling against MLB pitching vastly outweighs any production in Triple A. Particularly since everyone in Triple is learning to throw an entirely new baseball.