There must be something wrong with the G650GS data. That 90+ mpg average consists of 2 tanks, a sixty-something and a 125mpg one. I suspect that the latter must be some typo or similar. And 2 data points are far from being data
That's my main problem with fuelly - people often abandon their logs after a few tanks, or even before the first one
The 'vanilla' F/G650GS is not a tall bike, though. The Dakar/Sertao incarnation is. I, for example, am definitely too short for them. Once I tried a DL650 (it's in between), and that was about the tallest where I could keep my soles on the ground.