I just tried Fable 5.2 side-by-side with Opus 5.5 on the same prompt and I think you're right, n=1 but with strong signal.

Fable got right to the point, had cleaner/better responses and reasoning for its conclusions, got less distracted with secondary concerns, and still showed signs of the cleaner writing style compared to Opus, which improved a lot with 5.5 but can still be hard to parse sometimes.

I will keep using Opus for implementation tasks (e.g. building web apps to explore model predictions) but I think I'll try using Fable this week for the real DS stuff. Thanks!