Was one of my first observations also, Boeing switched from their "old" flap philosophy to much smaller and less slotted ones (as Airbus does since A320), but does not compensate for the lower lift by aileron droop. Was a little strange to notice.
Load reduction may be one issue, the other one that came to my mind was lateral controlability. More negative ailerons give better lateral stability and higher aileron efficiency. I am still curious how the raked wingtips with no leading edge devices on a large portion of the outer wing will perform during low speed test.
Maybe it was a precautonary measure to keep a larger stall margin for the outer wing before all aerodynamic asumptions have been verified ?
I am quite convinced that later on we will see aileron droop on the 787.