I don't know what problems you're working on but Fable is not just better, it is a step change from GPT 5.5 in my experience. It feels at least one major model generation ahead.
The fact that a review helps does not prove the model choice for the review.
You reviewing your own writing helps too!
Note, this is better than it was with Opus, where it was more like 90% of the time the Codex plans were obviously better.