[Yoda]

Delivery speed is so important, and uphill puts tend to move away from the hole as they slow down, where as downhill puts tend to move towards it, so, to combat gravity and slope, uphill puts might tend to enter the hole with a bit more speed. Maybe.

Other than a dead straight putt, all putts aimed directly at the hole tend to move away from the hole as the putt slows on a planar green (sloped back-to-front). That movement will be either left-to-right or right-to-left, depending on which side of the Zero Line (the straight putt line, either uphill or downhill, per Aim Point theory http://www.aimpointgolf.com/aimpointtv.html.