Performance optimization is different, because there's still some kind of a baseline truth. Every knows what a FPS is, and +5% FPS is +5% FPS. Even the tricky cases have some kind of boundary (+5% FPS on this hardware but -10% on this other hardware, +2% on scenes meeting these conditions but -3% otherwise, etc).

Meanwhile, nobody can agree on what a "good" LLM in, let alone how to measure it.