Comment by InsideOutSanta

> If you have specific complaints about the text and content, bring those up instead

Accusing text of being written by an LLM is a specific complaint about the text. It's shorthand for "the text is overly verbose and uses the typical clichés LLMs are known for, which makes the text unpleasant to read (it's too much text and too many empty clichés) and also makes me distrust the text, because now I'm not sure anyone even looked over it and made sure it says what they wanted to say."

It's just shorter to say "this sounds like it's written by AI."