Maybe if LLMs were aligned for this specific task it'd make more sense? But they're not. Their alignment tunes them to provide statistically helpful responses for a wide variety of things. They prefer positive responses to negative ones and are not tuned directly as a detection tool for arbitrary categorization. And maybe they do work well, but maybe it's only a specific version of a specific model against other specific models hiring material outputs? There's too many confounding things here to not have to study this in a rigorous way to come to the conclusion that felt... not carefully considered.
Maybe you have considered this more than I know. It sounds like you work a lot with this data. But the off-handedness set off my skepticism.