It isn't often that you see both riders on a motorcycle sustain nearly identical injuries (with the exception of head injuries).
I'm skeptical about the article's claim this was a high speed crash. While they're obviously in shock, they both seem to alert. They are also lying on the ground in close proximity to each other with no other obvious injuries (despite not wearing helmets) .
To me, it looks like they were traveling at approximately the same speed, but were directly beside wheel well and the bus driver didn't know they were there.
In all likelihood, the bus made contact with the left side of the bike. The instant the tire touched their legs, their legs were simultaneously pulled the up into the wheel well with enough force to essentially separate the limb at mid femur before they even came off the bike.
This would also explain all of the blood spatter at the top of the wheel well.
That is why I believe that the speed of the motorcycle had little to do with these injuries. Rather, it was subjecting their left legs to the massive amount of torque that is generated by a rotating tire of a moving bus.
Excessive speed implies it's the biker's fault. I suspect that the bus driver probably bears much of the responsibility for what happened.
Good eye. I showed this to an old colleague/friend that works in forensics and he agrees.