What are the aerodynamic design principles behind the "supersonic" propeller of Luigi Colani's C-309 racing plane? One of Luigi Colani's designs that is particularly confusing to me is the second design iteration of the C-309 propeller racing airplane. Allegedly, its two propellers are designed to be supersonic and they have a very peculiar shape, as shown in the photo below.





The leading edge of the C-309 propellers is both forward-swept and twisted in a circular fashion, given the propeller blades a helical appearance.
This is a very different approach from real-world supersonic propellers found in e.g. the Republic XF-84H Thunderscreech.

Assuming the propeller material to be indestructible for a moment, and that the propeller design is not guided by aesthetics alone, what would be the aerodynamic reasoning behind creating a propeller of such an absurd shape? Is it equivalent to a forward-swept wing that takes into account the relative velocity from the propeller rotation?
Looks like the Colani Museum has picked up my question on Twitter and posted a response later with an archive photo of an advertising article:



The English part of the article says about the propellers:


  Since 1976 we have been investigating sharply cambered pusher and tractor propellers which maintain supersonic flow over part of their top surfaces.


In contrast, the German translation says:


  Since 1976 we have been investigating strongly forward-swept pusher and tractor propellers.


So this sounds to me like they were simply looking to develop strongly forward-swept propellers with a supercritical airfoil. Aesthetics almost certainly also played a role in the design.