I dont think people (in this context) are suggesting replacing the junior developers with AI, but to treat the AI like a junior: to be clear with what you need, and to be defensive with what you accept back from them; to try and be conscious of their limitations when asking them to do something, and to phrase your questions in a way that will get you the best results back.
They might not be but using language which equates these generative LLMs with junior developers does allow a shift of meaning to actually equate juniors with LLMs, meaning they are the interchangeable, and therefore generative LLMs can replace juniors.
