It's not just patterns like "not just X, but Y", but also deeper patterns and a kind of narrative cadence. Sure it's also mimicking something real, but usually it's a mismatch between the insightfulness of the content and the quality of the delivery. It feels like chewing on empty calories, it's missing the intentionality and the edge of being human. I guess you need to read a lot of LLM output to get a feel for this beyond the surface level pattern matching.