I think Grissom might have been viewed as SS depth, before he got hurt..
With the limited winter spending budget Brez had, it's no wonder he didn't go all out for a 3rd string SS.
While thinking we could have had better than Reyes and DHam makes sense, too. There is only so much a GM can do to plan for injuries and injuries to your #2 guy at any given position.
The plan last year failed, but nobody expected Kike to be that bad on D, and Mondesi to take the whole year off. Bloom did have a plan B and C, but they just failed. Reyes was an afterthought (Remember, Cora was fully confident in Kike at SS. He even kept him there after he said he was not going to be the SS, anymore.
I think Brez is waiting to find out how long Story will be out, before making any move. He may end up not making any, even if Story misses 3-5 months. A lot might depend on how they view Grissom as a FT SS..