I'd guess with ever smaller boats fitting ever larger engines (think RIBs and Bass boats) the thinking may be that this format tames the prop torque and possibly gives more grip? That said, I know a man who is giving serious consideration to sticking a pair of these bad puppies on a 10m RIB.
The downside is that lack of propwalk means a single will have to be berthed with a bit more "attitude"
I'm not sure why the raised eyebrows? - this stuff has been standard in outdrives for ages.