I contacted a former collegiate summer ball teammate who's now a college head coach. He's coached his program to a national championship. His son plays pro ball. I asked him what effect he thinks preteen ball has on playing high school or college ball.
His response was "Absolutely none at all." Then he reminded me of a conversation we had a little over a week ago. He said my son would be a significantly different player his junior year from his sophomore year based on physical development and advanced coaching. "Therefore, why would what he did in LL or travel at that age matter?"