That study, if I remember correctly, only focuses on the aerodinamic aspect of the setups, but bikepacking is also known to be lighter because the bags are lighter than panniers and racks and also because it's tied to more minimalistic setups.
The point here would be sacrificing comfort, both camping and in ease of packing to increase performance, because you have a lighter bike that holds better in bumpy terrain.
Also, in a bikepacking setup you'd want your stuff ordered by density like:
High density --------------> low density
frame bag -- seat bag -- handlebar bags
With fork cages ussually used for a specific purpose because they are better carrying cilinders.