Holding back for sports reasons only is a sign that your son cannot compete on age-otherwise why would you do it. This creates bad feelings.
Fool. By your faulty logic, colleges would not redshirt players. Go learn some things and come back once you understand how most players make top D1 teams (and not just in lacrosse).
Most D1 hockey players play a few years of junior hockey for this very reason - because they can't compete with players who are starting college at 20 or 21. That is how the system works. You can whine about it or you can play the hand you are dealt.
You parents who whine about holdbacks and pound your chests about how your kid can compete with one-age kids are a laugh riot. What's the long game here? Playing on-age? Making mommy and daddy proud because junior can play with his peers? Good luck.
If being a top recruit at a top D1 program is the goal, do your kid a favor and hold him back. He will have more time to mature, grow, and improve his play. College coaches don't care about your kid's age or how well he competed on-age in middle school.
While you are whining about holdbacks, my kid will be talking to D1 coaches. Now hit the wall!
