That's the flaw in RLHF: constructs tagged as effective or sophisticated speech become templates, are increasingly used out of context (e.g., "not just A, not just B, but C" is usually meant to provide some synthesis and further the progress of the text) and suffer from significant overexposure. (And gone is the em-dash…)

It's bad in and of itself the way LLMs use it. They separate it into a weird declaration when it's usually something you'd say at the beginning and/or end of a paragraph or passage where you're making a case for that statement.

It's part of how LLMs often seem to repeat the same thing over and over again. Most arguments are X is Y (and the others are X is not Y, or X is likely Y), and LLMs lean on "X is Y" because it is the most distilled form of that argument - a thesis minus the meat. Also "This is not a Y, this is a Z."

They're just thesis sentences inserted in inappropriate locations. The reason it makes them overdramatic is because separated from the argument, they seem like they should be premises. Conclusions without premises have the feeling of demands.