It's just as possible for a pitcher's control to increase as his stuff. No guarantees, for some guys it will and some it won't. For most it won't, but every once in a while, you'll get lucky
I don't know for sure if height matters, but given that taller pitchers are known for sometimes taking longer to develop control in real life and that OOTP tries to imitate real life, I wouldn't be surprised if it did make a small difference.