It sounds ridiculous, but that flailing is a way to hold your position static while finding where you're going to land. Right before he does he goes coffin (if your arms and legs are splayed you'll break them, collar bone, neck fractures...). He knows he's going down hard regardless, but at the last fraction of a second he rolls his body over and goes coffin, trying to spread the impact over his whole body.

I'm sure he was hurt, but he did just about the only thing he could do without popping his drogue chute.