Average ratings are based on the published values and not the values entered in your own log entries.
Other than doing Hill of Life reps, this trail is the best way to get a lot of elevation gain in a short distance (and it's a lot less boring than going up and down the HoL as nauseum.) Note that I studied both my GPS log as well as the one on this site in Google Earth by clamping the elevation to ground height (the height measured by the keyhole satellites, which is a lot more accurate than taking the elevation recorded by the GPS.) This consistently gives 1400' as the total ascent/descent for doing the main trail out and back. My GPS reported around 1300' as the total, which is at least in the ballpark. In any case, definitely not 1800', but still a significant gain over the course of a 5-mile hike.