Two other possibilities: fit and fitness. Perhaps your riding position on the Secteur is more conducive to spinning than your KHS. Or, perhaps you are more accustomed to cycling, and your comfortable cadence has increased.
Simple experiment, if you've still got the KHS: take 'em both for a ride on a similar route, and see if you still mash more on the KHS, or if you're now spinning about as much on that bike as on the Secteur. If you're still mashing on the KHS, I'd say it might be fit issue. If not, then probably fitness.