I'm in the same place as you on this. My paternal grandmother was born in Norway and all of her ancestors going back to beginning of 1700 were from rural parts of Norway.
My ethnicity shows 7% Scandinavian, so I registered more than you. But I still wonder why it is not higher.
I also have 59% Central European and 30% British Isles, so I figure that some of the Norwegians are of mixed ancestry with either the BI or the German. But it must have been a long time ago.