The problem is, if you are suggesting team turnover is the reason why you win or lose, you are confirming what most believe. The reason for private success is the ability to get certain kids to play on your team. You can't have it both ways. Moving up a class and can't win a playoff game two years in a row is not indicative of a top notch coaching staff.
"not win a playoff game" isn't even the standard. Merely not trophying twice sends a team back down to their natural non-success factor enrollment.
I don't understand the apparent shot at coaching staffs here. The reality is a two year run could be "one really strong class". That's inherently true of any type of school regardless of how they get their students (public or private).
If it's meant to be on transfers/recruiting which seems to be the clear implication,
you could totally do that. "Your sports recruitment efforts are clear and a clear effort to compete at a number higher than your enrollment (already multiplied) and so you will play at a higher classification" isn't a particularly difficult logical claim to convincingly argue and not that much harder to implement a metric around if you wanted. Then teams would be measured in a way that is fairly transparent and doesn't presume success equaled unfair competetive grounds (two years later).
"You did too well because you had a two year run". Clearly not the same message. It's basically outright presuming success wasn't fair or even. It sends kind of a perserve message about success and sportsmanship. It's a very far cry from something like Premier league promotion/relegation which is a recognition of success. It's very clearly about people being unhappy about any sort of sustained success and crying "unfair".
It isn't even comparable to something like a chess Elo ranking where the
same competitor retains a talent score that matches them up to opponents according to talent level. It's just a lame attempt to punish teams who are "too successful" despite following a set criteria of competetive balance.
There's plenty of success based classifications in sports/games and this success factor isn't like one I can think of in merit, intent, or functional design.
Argue the classification criteria all you want, but once those are set and schools comply, don't move them up or down on a two year trailing success cycle that stops being relevant the second it's in effect. Just make sure the rules and criteria are being followed and applied and the best should win.