GPT 5.6 Sol and Fable are similar step changes, not 5.5, but that's beside the point. If in the Markdown instruction files you ask them to periodically clean up the code or refactor where necessary then that's what they'll do. They don't explicitly do it because otherwise people, as they had for previous models, complain where models are asked to change one thing then they rewrite whole systems, so now the latest models are explicitly trained on instruction following.
In other words you can make the AI act like a software engineer complete with fixing and improving code autonomously (Cursor gave a glimpse of this [0]). It is not a failure of the model to do this automatically but a failure of the human having the wrong instructions.
i guess to clarify my contention:
generic prompting like "review this code" or "make the architecture better" will raise the floor but cannot come close to human-quality code without humans understanding what code exists and what to ask for.
Obviously cursor and other labs have a stake in this going one direction, but I don't buy it, and I don't think you should either.
In fact, "Rebuild sqlite from spec" has all the problems with every other benchmark that I cited - model knows the whole problem up front and never has to iterate on the pile of slop it created cheating its way to a solution.
In any case, politely, I think we're mostly arguing vibes here and I'm not sure its going to get anywhere.