While this review is clearly either misstated or the helmet was defective, lets think a little more analytically about how helmets work.

First, when your head hits something, with or without a helmet, 100% of the energy is going to be transmitted to your head, unless there is some sort of damage to the helmet. The benefit that the helmet gives you is that is dissipates all that energy over a much longer time than would have happened without the helmet. Also, a helmet breaking in half, cracking, or crumpling all have the effect of transferring some of the impact energy to deforming the helmet, much as crumple zones in cars do. A helmet also spreads the area of impact and lowering the pressure on your head.

My point is that here are all sorts of complicated interactions going on during impacts, and helmets make it even more complicated. Assuming that the helmet was defective because it broke or crumpled isn't very rigorous, and head injuries are so complicated that saying a "minor crash" should or shouldn't have given you a concussion is too hard to analyze as well.