I'm confused by what I see in the pics. You said it was bare gravel that he lost control in, but there are black tire skid marks from front & rear tires indicating a solid surface (maybe with some fine gravel on top?). Whenever I have locked up wheels in gravel, it just pushes the gravel out in front of the tires, leaving a fine white dust trail on the ground where the skid was.
The important thing is your buddy will be ok after a bit of healing, ready to ride again I presume. Good thing he was geared up. Kissing the ground, whether asphalt or gravel is never fun.
2018 Yamaha FJR 1300A
2014 Honda CB1100 DLX
It doesn't matter what I ride, where I ride, or how far I ride... it only matters THAT I ride...every day. "Ferret"