and how exactly is this a coverup ?
The coverup is that back when this happened, the elders of the church arranged for the perpetrator and the victims to receive counseling rather than involving the juvenile justice system. The second stage of the coverup was when a state trooper was informally involved and he failed to act in a timely manner once he received information of a criminal act. When in 2006, the allegations finally made it to the Springdale PD, the statute of limitations had expired as the involvement of the trooper started the clock. The elders may be able to weasel out of their obligation to report abuse as the statute says 'clergy member', but a police officer who is informed of a crime against minors doesn't have that option.
The outcome would probably not have been any different. Juvi authorities would have sent Josh to counseling and it would have been expunged once he reached the age of majority. By all accounts, he managed to move past this, no reason to believe that the outcome would have been any better had the juvi authorities been involved. They are notorious for their f###-ups, so I can understand why a religious community would try to handle this internally. But then again, when the catholic church handled their abuse problem internally, everyone got upset, so I guess there is no way to win this one.