My son is a 2018 that played on the Crabs U13 team two years ago and half that team was between 5'9" and 5'11". They could have passed as a basketball team in comparison to most teams and there were no holdbacks on the U13 level two years ago. If you are attracting most of the best players within a 50 mile radius, they typically are going to be more advanced than the average kids. "Bigger, Faster, Stronger!" Then you throw the holdbacks into the current class based scenario, having 6' kids in that class is understandable.