Originally Posted by alan s

Easy win. The wheel is standing on the rim, not the spokes. The slight detensioning of the lower spokes is due to rim compression and deformation.

Edit: Looking at the front end of a bike, the load of the rider, gear and bike compresses the fork and axle/hub, tensions the upper spokes, and compresses the rim all the way around to the ground. The lower spokes are detensioned slightly, and mainly serve to keep the wheel as round as possible and resist lateral forces. The rim compression and slight deformation is concentrated at the point where the wheel meets the ground, which accounts for the noticeable spoke detensioning there.