Interesting situation. More testing is required to determine if this experience was a one-off, or consistently true. About 10 years ago we fit a seasoned domestic pro using power meters and video. 4 weeks later he came back with real world results that were disappointing, and we changed the fit back to what he had been using for some years.
Point is that sometimes a fitting does not translate to efficiency in application. More riding is needed to determine what gives here.