If not an abstraction, how would you describe it then?

I don't know? It's an agent, an automated contractor, a black box that produces work. When you pay someone to help write your app, you don't call that an "abstraction."

AI isn’t someone. And sure instead of building X I can of course bring in Y that abstracts away X.

I think the reasonable way to look at LLMs is similar to how you'd work with junior developers. They can churn out code, but do need constant guidance. Of course, (some of the) real juniors will eventually become seniors. It remains to be seen if LLMs will.