Just for arguments sake try to consider this scenario from an entire cross section of the situation.
1) most of the time arguments like this are based on the assumption of a kid being what you would consider to old for the grade. Not fact.
2) for every kid that is winning matches in this scenario, there is at least 1 that isn't winning many matches at all even against what you would consider younger competitors.
3) some kids are just more athletic, more dedicated, better at learning and applying, more coordinated, better coached...the list goes on.
4) age doesn't directly translate to winning. Just the same as cutting weight or being ranked higher.
Something to keep in mind when arguing this is no arguments are going to change your team or individual success.
When my oldest son was a freshman high school, we were considering wrestling at college open tournaments starting in his sophomore year. After his freshman year, the NCAA banned competitors that were enrolled in high school or younger from competing in these open events. The reason for this is because a kid that was enrolled in the 8th grade won one of these open tournaments. That is fact. The moral to this story is that all wrestlers are NOT created equal. Some are just better. And age has less to do with it than you are comfortable admitting.
Be careful stabbing into the dark. You may not hit what you think you are stabbing at.