I would not trust this system too much; yes, it eliminates a hole in the hull
as well as need in stern thruster (not common on sailboats, IMHO)
BUT: in case of "catching" something underwater you loose propeller plus
a real expensive electric motor
(might be a set of total ~$7000, if feathering prop),
with poor chances of replacing it fast.
Rudders ... are no longer required © FischerPanda
I'd like to see the author in a rudderless boat 300 miles away from the coast
In any case you have to protect these units from all sides VERY well.