It would be interesting to know whether the increase in head trauma stems from single accidents being inherently more dangerous on e-bikes and that being the increase, or if e-bikes make biking more accessible bringing out less experienced bikers on the road where they are subsequently struck by cars.
It's not possible to see the study without a subscription, so it's hard to tell.
I'd not be surprised to see the latter being the case though, cars are the biggest predator when it comes to bicyclists.