That doesn't seem like a very good metric to me. There's no way there's any single number that can properly compare driving deaths between countries, but shouldn't this at least be normalized to account for number of drivers? Like what if Finland just has a lot of long, empty roads? Also doesn't there need to be a comparison within the German data on deaths on roads with and without speed limits?
But traffic density would be another interesting metric. Temporary speed limits on the autobahn are typically dynamically adjusted to the traffic situation.
Eventually, I see so many other factors that could enter the picture that I’m wondering if that comparison makes any sense at all (apart from proving the writer is trying to force his point?).
There is lot of highways though. And those can be middle of forest with 80 speed limit. So losing control and hitting upcoming traffic or tree is much more likely.