I think people and organizations will find ways to try to get around any law, but I think in this case the act of charging someone with failure to report is significant in itself. Once the charges are out, the individual (and the organization, most likely) needs to respond, and any attempts at legal maneuvering will be reported. With the WTS, you can be sure that they will get involved immediately in order to protect itself, and hopefully this is where the media spotlight will be shined.
We know that CSA happens and that it happens with horrifying frequency. And we know that there are organizations -including some large religious organizations- that are so determined to protect themselves that they will discard any notion of justice and leave victims strewn about. The most effective way to deal with this problem is to shine a bright light on them when they are acting this way, to shame them into putting the safety and health of children first. The goal is to get these organizations to make it a clear policy to their members-- always report it. The child comes first.