Its not the concussive blows that are the only detriment, though. Repeated blows are part of the concussion spectrum, as well.
Sure those MASSIVE collisons, maybe the guardian cap doesn't prevent those individuals from being concussed... But there is simply no way, over time, a padded surface isn't consistently better than one that isn't.
I'm also very confused by the Stanford article you post that has quotes like this... FWIW-- they only tested collusions that are head to head..
"The researchers were hesitant to support the cap, which costs about $50, but they noted that it's possible the cap provides some protection."
"but on average the caps provided 15% to 20% more protection than blows to the head with only a helmet." Granted, this was based on one particular type of blow.. but still
In my eyes, when we are talking about REAL people and not numbers... idk how you can read those two quotes and not say "Guardian Caps work". Literally.. "some protection" should be enough. Working doesn't mean "full proof".