I am not sure if the thinness is considered a complication or not. I read somewhere, however, that there are something like seven or so big horological challenges (e.g., the chronograph, perpetual calendar, repeater) among which is included the ultra thin movement. So while it may not be considered a complication, it is certainly an important achievement for any manufacturer to create an ultra thin movement.
As Steve more eloquently said above, JLC's achievement with the 34mm MUT and the 849 movement is manifold, but not the least of the achievements is the robustness of the movmement and the watch when compared to other ultrathin watches. The MUT can actually be used and withstand the abuses of daily wear.
Long live the MUT!
respo