I have to imagine it took a lot of work to verify conclusively whether something was or was not generated

The study is by a company that creates software to detect AI content, so it’s literally their whole job

(it also means there’s a conflict of interest, since they want to show how much content their detector can detect)

It’s a much larger sample size than a lot of studies.

It’s an extremely small proportion of the total number of Facebook posts though. Nowhere near enough for statistical significance.