Graterol's not getting to 120 no matter what they do. By the time he got stretched out, the minor league season would almost be over.
And regardless of whether he gets to 120 or 80 or whatever, he's going to be on an innings limit next year. So you might as well use him for the best leverage you can.
I'd think they could get him pretty close to 120 if they sent him to play fall or winter ball somewhere.