Aerodynamics is a weird voodoo science. Everything gets non-linear so fast in a moving compressible fluid. Sometimes a smooth surface can be draggy, where a sharp one isn't, just because a bump upstream from that location causes a vortex that needs to be disrupted. Sometimes a small divot can improve performance radically because it moves the flow boundary away from the surface.

I wouldn't be surprised if some Aero Wizard came up with a way to make a brick aerodynamic with some magic ducting and a spoiler.