My guess is the blade shape is compromised by the construction method. Looks like it has symmetrical blades with no cup (good for reverse) which bulge out at the top so they can fit a large metal shaft in them to stop the plastic breaking.
I would still be very happy if I had one on my boat
, but after seeing the test I would not choose one when it costs $2K.
Possibly the prop was the wrong sized and not pitched well? But the size and pitch
was in the same ranges of the rest of the props tested.