But they aren't aware of the prior article?! Bs.
As someone working with Scandinavian registry data I claim that one generally has a pretty good idea who has used the data before and for what outcomes. With a low probability, maybe staff at the stats office has turned over and didn't pass on the knowledge about the old article, but these people have life contracts, so I really doubt that.
I think the newer article's authors were aware of the older contribution.