I think this was the plan, but a few things happened.
Torres never got better. Short is basically the right handed option. Remember he was DFA'ed, but then brought back once Torres had to go on the IL.
Around that time, they signed Paul DeJong, who could very easily be a better option than Short. Hell, you could probably call him up right now if you wanted to... except, he's out for the year with an injury now.
Trei Cruz is still on rehab, and wasn't exactly banging the door down in AAA before his injury.
And now Torres had a setback.
So now your primary shortstop in AAA is Max Burt, who they tried to send to AA before having to drag him back up when DeJong was hurt. Burt is a fringe guy with a career minor league OPS around 0.600. It's not some indictment on the org that he's their AAA SS right now. It's just been injury after injury after injury. Heck, Jack Penney, who was playing with the squad late in camp is just now getting his rehab going.
Hard to say if the injuries are bad luck or if something is afoot with the strength/training staff.