No proof. Why change it? I love it when the publics win the Super 8, or at least get real close, like when Reading rolled to a super 8 title and pasted three Catholics to win a few years back and then Hingham did it. Not many private schools can lay claim to a super 8 title. St John's just won their first one last year. MC was never in it until their modern dynasty, Cathedral/Pope Francis never has, nor have most private/catholic schools. Meantime, a town team like Reading has like the fourth most Super8 appearances of any school in its history. They rarely win, but publics can and have won it, and it makes it all the more sweeter when they do.
If anything, get rid of the stupid tournament and run the north south brackets like the old days. The two best teams always rise to the top
Ok, to your point. Every so often a public team comes along and competes and on a rare occasion wins the Super 8.
By separating the Public and Catholic Championships and allowing the Champions to play each other at the end of the year should settle the debate. This way the Public anomaly will surely roll through the Public Championship and have the opportunity to win the whole thing.
Minnesota has the best and purest system, although things have changed out there in recent times.