No, he's right. It's essentially impossible to make a statement about what the outcome "would've been". Is it more likely than not that it did SOME good? Absolutely, no question.
I wear a helmet. However, I don't walk around with a false sense of security thinking that it's a magic forcefield.
Have you ever read the label inside your helmet? If you're not wearing a moto x style/Seth style full-face helmet, the truth is that the helmet is rated to about 20-25mph. It's also good for one SINGLE impact. Do people realize that? So, if you've hit your head, stood up and said, "thank god for my helmet!", I hope you replaced it because that helmet is done—that's whether or not there's visible damage of any kind or not.
The manufacturers straight up admit that the helmets produced for skiing aren't adequate in preventing concussions, brain/brain stem shear injuries, secondary impacts of the brain rebounding against the opposite side of the skull, rotational injuries (I saw some video where POC was testing a helmet designed to combat this specifically, not available I don't think), deceleration injuries, etc. What they do prevent is Lac's and potentially skull fractures....potentially.
So, if you're hitting big kickers, mobbing groomers at 50mph, skiing a tree line, and are convinced that you're good to go, well, you're not.
Everyone's slaying this article, questioning the conclusions, etc. The problem is the author NEVER claims a definitive causal relationship, nor claims that helmets are worthless. The author simply presents that though helmet use is up (I think it said 70% since 03? I didn't reread the article before this post), head injuries remain static. She also points out how advances in equipment, access to more challenging terrain, the development of bigger and faster parks, and the increasing thresh hold of acceptable risk taking in many are all inter-related.
Honestly, if you read that article and your takeaway is "helmet's don't do shit, there's no point in wearing them!" you're fucking stupid. Try reading it again without a scrunched up face and taking it personally because you've been helmet crusading for five years and have convinced yourself that the only reason you're alive is because you wear a helmet.