That’s exactly the point.
In Norway and Sweden, unlike Germany, there is a huge amount of empty land.
For this reason it doesn’t make sense at all to compare Sweden with Germany when you have a far, far better comparison in the nearby country.
If you have a hypothetical country with a huge swath of empty land, and a single city with the population density of Hong Kong, the population density of that country will appear to be low, but in fact all the people living in the country live in a highly dense city. Perhaps a better measure than population/land area would be the average of the population density in the square kilometer surrounding each inhabitant (or something like that).
That’s exactly the point. In Norway and Sweden, unlike Germany, there is a huge amount of empty land. For this reason it doesn’t make sense at all to compare Sweden with Germany when you have a far, far better comparison in the nearby country.