I think what the parent poster is getting at is that "LLMs don't sound natural". People don't write the same way an LLM does, which leads to a kind of 'uncanny valley' effect when reading AI text.

Over time, I suspect both human and AI writing will 'converge'. Humans are good at adopting/imitating language from a variety of sources, so I won't be surprised when we start using "load-bearing" in conversation. Simultaneously, LLMs will start sounding more natural.

That's in fact not what they said, though.