Because writing is a dirty, scratched window with liquid between the frames and an LLM can be the microfiber cloth and degreaser that makes it just a bit clearer.
Outsourcing thinking is bad. Using an LLM to assist in communicating thought is or at least can be good.
The real problem I think the author has here is that it can be difficult to tell the difference and therefore difficult to judge if it id worth your time. However, I think author/publisher reputation is a far better signal than looking for AI tells.