We can't know for sure, so it's best not to attack like this. All we can really say is that the posts were getting classified that way.
There's also a large fuzzy area these days where people are using tools to edit, "polish", etc., but do not think of it as using an LLM to write. This is particularly the case with non-native English speakers.
A few recent cases where this sort of thing came up:
https://news.ycombinator.com/item?id=48467726
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