Grav,
The drooped tip adds downward speed to the shed vortex so that it pushes the vortex away from interfering with the next blade, the aero guys said. It also minimizes the vortex energy to some degree. It is akin to the upswept tips of fixed wing jets.
One aerodynamicist told me not to hurt my brain understanding why these things work, there is no rule nor reason. It is nearly trial and error, but at least now the trials are relatively cheap CFD runs of various shapes.