I think harnesses would count, AI != LLMs. Any piece of code that helps the computer reason for itself is AI, the harnesses are AI in a sense.
People are specifically talking about the engine itself and not the tools used.
We wouldn't call humans creating a calculator "recursive self improvement".
By that interpretation, neither the harness nor the LLM is the AI. The computer (or system of computers) taken as a whole is the AI. You can't remove any piece and still have an intelligent system.