This sounds like an old "Hobie" argument about sailing around the course with one or the other rudders always out of the water! (only one at a time) It seemed that the loss of positive steering control cost much more than any "percieved" reduction in drag.
The pro's and con's of this "so called" rudder drag etc was fully investigated and resolved through full practical experimentation by C. A. Marjac before 1964, and I would suggest that any company that is trying to "sell" a product to eliminate this drag or, even more, use a system to gain speed out of some "so called" phenomina. is selling, not a successful system but a "bill of goods"
Just my opinion
Darryl