Virtually all those blows could potentially unseat a horseman, cause a serious whiplash injury to the neck if unexpected or cause a concussion that might dizzy someone on the spot, knock them out cold, or might not become apparent until migraines start a week later. I can tell you from experience on the receiving end, that even a fist to the temple, with both fist and head padded can knock a person out cold.
Any blow hard enough to dent a helmet, is hard enough to cause a brain or head injury. Concussion is about the brain moving inside the skull, not about the literal trauma to the surface of the head. Motorcycle and bicycle helmets mitigate, but don't prevent concussion injuries in many cases and they have a lot more shock absorbent liner materials than these helmets.
So even without an actual cut injury, a rider in this helmet has a good chance to be 'one hit' to unconsciousness with any significant blow from a bladed weapon of any sort.
That aside... I really don't want to experience an axe blow. Not yesterday. I wonder if in game, this means that blunt injuries (non killing) should be more prevalent, and cut injuries less?
I feel like for example, on horse I kill more people with a glaive than I do with a lance. But I would suspect that should be the opposite. That the glaive while brutal at cutting, should be more of a blunt force weapon as per above when confronted by good armour. The lance on the other hand, as a single point of impact weapon, should probably kill a decent chunk of what it hits at a charge, armour or not.