I don't understand the advantage of this. Surely it must exert the same forces as the usual shaft-mounted propeller, and therefore require bearings of the same

I don't understand the advantage of this. Surely it must exert the same forces as the usual shaft-mounted propeller, and therefore require bearings of the same strength? What's the advantage? Is it something to do with the load being distributed all around the rim instead of concentrated at the center?