There is no difference between spinning the heatsink and moving air at the same velocity across stationary heatsink fins. It's about molecules of air at a lower temperature going across a surface with at a higher temperature. N molecules per unit time "absorb" some of the heat and come of of the process at a higher temperature. The surface temperature drops by a similar amount.
What kills you in both cases is a very thin boundary layer of air that sticks to the surface and has a velocity profile that goes from zero at the surface to whatever the air velocity might be. This boundary layer isn't good for heat transfer from the surface to the moving air molecules, which takes a toll on the overall efficiency of the process.
There are techniques to help break-up the boundary layer in stationary fin heatsinks. Some break-up airflow to introduce turbulence. Others use raw velocity to break it up (air impingement cooling).
I don't know how well the rotating aluminum impeller breaks-up the boundary layer surrounding the fins. It won't eliminate it completely but it certainly could be much improved from the case of stationary fins with low-speed air going across them. If you had a heatsink with stationary fins and air moving at the same speed as in the case of the rotating impeller (by using fans, of course) you'd probably get similar boundary layer effects.
What I learned is that there really is very little magic in heat transfer. I have seen some really wacky ideas brought to market that always seem interesting but have never proven to beat the simple solutions. Funny enough, other than materials, most of the focus is always around dealing with the boundary layer, an issue that disappears (in terms of its significance) once you move into fluid-based cooling.
Caveat: I have not studied rotating aluminum impeller/heat-sinks, so I could very well be missing something that I simply don't know. My opinions are based on thousands of hours of research and FEA work in looking for solutions for the aforementioned project.