I love watching the JW cart crashers on YouTube and how the zombie, brain dead, we are so much better than you JDubs react. When they do talk a little about the two witness rule they will mention the need for proof and the testimony of the poor child is just not enough to take the inquiry any further.
The reason for calling the police is immediately is that DNA can be gathered from the poor victim. This evidence is the second witness used for prosecution. The elders will first call the Headquarter's legal department for direction and then set up some meeting with the victim on a nonmeeting night. Valuable time has been lost for DNA collection. The Witlesses don't want a second witness and want to sweep this under the rug to avoid bad press.
The second thing is that if the JDub pedophile confesses and is disfellowshipped and the police are not involved, the Witlesses have knowledge of a pedophile that is now free to take advantage of other "worldly" children and become his next victims. I guess the Witnesses reason that is not our problem and the children are going to die soon anyhow by the loving God Jehovah. Even when a pedophile has been disfellowshipped and wants to return to the Borg, the congregation is not even made aware that a pedophile is in their midst.
The JDubs are one crazy, godless, cold-hearted cult.