Because the learning rate vs. pre-training is completely different. This is not accurate, but my mental model is that the LLM's initial training establishes the

Because the learning rate vs. pre-training is completely different. This is not accurate, but my mental model is that the LLM's initial training establishes the "space of concepts and ideas" while tuning (like RLHF and fine-tuning) changes how it expresses those concepts and ideas. It works well for me in deciding my approach.