You look fastball because you can ajust to the offspeed looking for fastball. If your mindset is to look offspeed then its over if you get gas. Yes my guys can hit offspeed fairly well. But we wont win many games with the mindset when we get in the box look hanging curve so we can hit homeruns.
As far as younger guys picking up on these advanced mindsets let me add this. I won a state AAU title with 11u a few years back. We were so more advanced than the other teams because I coached them to death in 1st third offense and defense. Bunt defense and bunt offense. Outfield cuts and double cuts. Leave the offspeed alone untill you have two strikes and hit the fastball. Most teams at the younger levels spend all their time fielding ground balls and taking bp. We spent our time broken down in three phases. Individual fundemental instruction such as fielding techniques, proper throwing ,catching techniques, pitching mechanics , base running and hitting including bunting. Phase 2 Team oriented: The above mentioned category 1st and thirds, bunt d and o, outfield cuts and double cuts and situations. Phase 3 the mental aspect of the game. Pitching for location and why. Changing speeds on fastball and why. Setting up hitters by pitching in reverse and forward and why. Hitting mindset having a game plan at the plate before you even step in the box. Now these kids were the cream of the crop talent wise in the area. They were more advanced talent wise than most kids their age. But I was amazed how much better we were than our competition that was just as talented. I know for a fact that kids will rise to the level that is expected of them. I always told them yes you are 11 years old but you wont beat the best 11 year olds by playing like 11 year olds. Im going to coach you like your 15. And you are going to play like your 15. And when you do those 11 year olds are not going to have a chance against you. And they didnt.