I have a feeling that people who shout this (I gotta be careful, I call out a bunch of articles as LLM-written) do not always know what to look out for. Em dashes aren't inherently LLM, neither are some of the phrases it uses.

One pattern I look for is; how is the end part written? Does it tie into the whole story? Is it extremely generic? Did the author put something real / raw / personal in it? If not, its a grey area, any other hints will lean my conclusion to real or fake.