Weird and distorted conclusion. "After adjustments for direct and indirect taxes paid," indeed. That's the whole difference: The Scandinavians have a much better taxation system.
I'm not sure what you mean, but the point is that Sweden has the weird habit of taxing benefits, something I think few other countries do. People who get, say, unemployment benefits get taxed on it. Thus, both tax levels and spending levels SEEM higher in Sweden than they actually are, since some of that spending is taken back through taxes and some of those taxes are on money already earned by the state through other taxes.
The studies conclusion is that welfare expenditures per capita are similar in the United States and Scandinavian countries provided you control for taxes per capita. But, of course, taxes per capita are higher in Scandinavian countries than in the US, so the benefits are not actually comparable, and the study is saying nothing meaningful.
By "better taxation system", I was just referring to the greater progressive-ness of the tax rate: higher top marginal rate, etc. I'm sure Scandinavian countries have their own weird tax quirks as well.