PIAA simply does not have the resources to investigate every potential allegation in every sport across the state. And that's a good thing. Rival schools would turn PIAA into the Sports Stasi, more than they already do.
If those resources existed, they'd still push on big school football and basketball. Other sports would get investigated with remaining resources, which is to say only the most blatant cases.
So it will always be up to the PIAA Districts to enforce locally -- translated, have unwritten gentleman's agreements for how much cheating they will tolerate among local schools. And if that means hypothetically D7 or D11 are more tolerant than D6, well, that's life
People can complain about that all they want but what's the alternative? Club sports only? Jungle thick bureaucracy? Everybody lawyers up?