Originally Posted by JackOlsen
As I've always understood it, head/neck restraints were created to fix a danger that is specific to full-restraint harnesses -- namely that by restricting the movement of the torso, 5/6-point systems create a deceleration mismatch with the head that can cause basilar skull fractures. A 3-point belt allows a tremendous amount of movement for the torso, so there isn't that mismatch. That's why basilar skull fractures are a thing in racing, but not in normal driving.
Have I been misinformed?
I asked this question to Joe Marco, the safety system guru, a number of years ago, and he agreed that three point belt/airbags didn't require a hans style device for the reasons you said.
Please note, I'm no expert, and no one should make decisions based on info from nameless people on forums.