I agree with you that Maxwell is like a JIT (with superoptimization inside of it: a very smart one which can propose smart things using the underlying agentic model, and reason about semantic equivalences to figure out what to commit or not) and that that is a natural analogy.

But people who write JITs don't call the overall process (original code, JIT) "self-improving code", do they?

What is the "self" in (original code, JIT)? Is it the entire process? But the JIT doesn't make itself better as it runs? Is all code that runs in a managed runtime with dynamic analysis self-improving?

A much better term might be "dynamically-improving code"

But related and to the point of my original message: the phrase "self-improving" has been used in vogue by AI research / labs ... and this is another example of something which is not a clear term, and seems intended for marketing