I couldn’t tell you how true that is. For example, Randy Johnson, back in the day his fastball was crusing, but could the hitters still hit good off of him? Yes. Now, lets say you got kid who crusies a ball in pretty well in 11U, he’s going to be hard to hit because when the kids looks at him they’re saying “Holy crap this guy throws fast.” And they are scared of him. Now, as you get older 13U - 14U you are able to have the mindset that, the fastest he pitches the farther it goes.
As they say, baseball is 90% mental and 10% physical.