A lot of things sound like a good thing. We don't want people trafficking drugs, so let's search everyone's home. Certainly Disney is a private operation and I am on private property when staying there. They just don't do a good job of indicating this intrusive check prior to booking. We still stay and endure it.
Disney resorts are peppered with security cameras everywhere. Certainly they would see suspicious things happening in the hallways and could tailor their checks to rooms where traffic in and out looks out of place.
If they had caught even a single human trafficker, we would have seen reports of it in the news. Even if Disney didn't disclose it, there are enough independent journalists and blogs that follow police reports from in and around Disney World that it would have come up. This is all public record.