TPM I have never said that relying on a CB stunted my son's development on the FB. I do say that relying on a CB doesn't mean you don't develop a FB. He also has great control of his FB usually like all pitchers. He had extraordinary ability to throw CBs against all levels of hitters including guys who played pro ball.
Young pitchers experiment with the CB. I see it all the time. Their teammate shows them how to throw it and they fool around with it. My son was no different but he had great instruction and the help of a high prospect who dated my daughter. He also had natural movement even on his 4 seam FB. I have seen a few occasions where he couldn't control his FB but that is very rare. There are also times when he has trouble controlling his best pitches. That is the nature of pitching.
I also tell pitcher to know their body. Shut it down when things feel funny and live to pitch another day. My son was probably slightly paranoid about injuring his arm. I actually thought that might have impeded his velocity. At 16 he was topping out at 83 and hasn't gained much velocity since then. He topped out at 85-86 this fall after adjusting his mechanics back to what they were. To me the most important things are keeping your elbo at shoulder level and good alignment. I also don't like locking the elbow out after relese as it causes elbow problems, Many hard throwers do this and get bone chips and other injuries.