I swear, the built in points estimator for FAHControl (and likely others, such as FAHMon) kinda stink nowadays.
I remember 4-5 years ago, in the GPU2 and 3 era, when all WUs worked under the same core revision. During those times, you could actually semi-rely on close-to-actual-production numbers. Now, with the addition of the 680 into my primary machine, estimated PPD is lower than without it. However, ACTUAL registered points (according to the Overclockers tracker) is higher than without it, by a fair/expected margin.