My guess is that the 12 wing rotors are at a fixed angles similar to a quadcopter V-tail. Unlike a v-tail, and to hazard another guess, I figure the inner 8 rotors point outwards to help provide stability so that a roll ends up with the lower side pointing straight down providing more lift and the higher side points out the side providing less lift. This pushes the craft back upright. There are times when you actually do want to roll so the 4 outer rotors point in. They're further out so there is more roll leverage. The mechanisms to tilt the rotors would add extra weight to a craft that's probably already low on margins. I'd say it's better to be a little less efficient for a short part of a flight than carry the extra weight for the duration.