I don't know, accidentally whacking yourself in the head with a wax wood 3SS makes it feel pretty f-ing hard. They can be rather heavy, and despite the flexibility the mass does make a difference. I imagine a full-swing, full extension whack in the head with one would be pretty debiliatating. Of course, harder/heavier woods would be even worse.
I agree that this isn't a battlefield weapon - one legend is that it was an improvised weapon which originated with someone's broken weapon on the battlefield, perhaps a normal long-handled flail or a spear or staff, who then thought "hey, that could be a pretty cool weapon if I did it right".
I also think sparring like this doesn't really display or reveal how effective these weapons could be. It is impossible to truly practice at full force with weapons, for obvious reasons. So what this shows us is whether or not someone could get in a hit with their weapon before the opponent closes with them. What the effects of that hit might be, we can only guess. But the sparring match then moves on to what happens if your hit was off target or you missed, and now have to get into close fighting.
So the best thing you can do is make sure you also drill with the weapon and practice hitting targets with it at full force with different techniques, so if you ever did have to use it, your first hit might be effective and avoid the close-fighting altogether. Practice fighting can never tell you that, because you don't want to risk incapacitating your friends and partners.