Nothing sexy about the 650 Rotax motor. Except that it's unbreakable, reliable, performs well and is frugal with fuel.
I think I'd rather have that than sexy.

Bwhahahahahahahaha!
Wait I'll take some pictures today.
I also have missed the "performs well" part to date. The F / ST were phlegmatic. The GS / GSD felt as if they had a bungee cord for a throttle cable. The G was an improvement apparently due to improved fuel management. Still nothing that blows my hair back.
I can see a X-Challenge vs DR race coming up soon!

It will be close!
G650X
144kg
39kw
60Nm @5200
Power to weight 0.1647417925
DR650
147kg
32/34kw depending on what model.
54Nm @4600
Power to weight 0.1324141252
I know which one stops faster though, and it's not Japanese

Just for interest sake, here is the KTM 690 specs.
138.5kg
46kw
65Nm @ 6550 rpm
Power to weight 0.2013004305
For those basing the Octavia's engine choice power wise on riding a F650 Rotax....I've ridden some a F650GS and 2x Setao's and I've ridden my XChallenge and XCountry and I will tell you that they are NOTHING like a F650. It's got 45KG's-50kg's and + 3KW on it. And I'm guessing this build is even lighter.
The 650 Rotax is nice and torquey, smoother than most Thumpers, frugal and as have been said, propel you forward with a twist of the wrist at over the limit speeds with a slight twist of the wrist (On the XChallenge/XMoto/XCountry) and relatively reliable. <--- all sexy characteristics in my eyes

Literally the only other road legal 650 Thumper that beats those figures is the KTM 690 and that technically closer to a 700 than a 650.
What more do you want from a Thumper engine?
So other than a basing it of a KTM 690 - what thumper engine that's more exciting would you have chosen to base a street bike on?
I think Hyde Designed deserves more credit for this. Hell It's really something unique and the guy is proud of it. What I wont give to be so creative and tallented when it comes to bikes. I hardly know how to torque a bolt.