Both QB's committed are from the high school ranks.
When you think about it, there's always attrition at the QB spot, so I think this is preparatory if anything else.
These two guys will assuredly redshirt their first year, so when they become eligible you'll have Stock as a RS senior, Urzua a RS junior, Banks a RS sophomore and Turner a RS freshman.
So...five QB's will be on scholarship vying for one spot after Stock leaves. If you ask me, it looks like a play to throw as many logs in the fire of competition as they can. Perhaps the staff isn't sold on Urzua or Banks based on what they saw this spring and they want to spark some competition to make everyone better. Or...they're preparing for a departure down the line.