Under your rendering, bogus calls made by unidentified third parties can be be used to trigger raids, which then turn into global fishing expeditions. Then officials merely say "Oops, not my problem?" Fruit of the poisonous tree.
You'd be surprised by how often that happens. If the "unknown caller" is a government agent, the evidence is suppressed. If not, the evidence gets in.
And no, they don't become fishing expeditions. But if a cop enters a residence (or area) under the authority of warrant derived from an anonymous call, any evidence of a crime (even a crime unrelated to the original complaint) visible to the cop gets in.
JuanCarlos is pretty much dead on. The sect can't argue that the girl faked the call and that justifies getting the kids back in the face of apparent child abuse. Those are separate issues.