Tananger is counted as part of the Stavanger/Sandnes urban area by SSB, so it might pop up in that respect here and there. But I agree with the previous question: how does this relate to OSM? Organic Maps show the Wikipedia entry for Tananger, which is quoted above. The quote continues: 

"The urban area is located on the west side of the Stavanger Peninsula between the North Sea and the Hafrsfjorden. It lies about 10 kilometres (6.2 mi) southwest of the city centre of Stavanger. "

This is from Wikipedia, though, not from OSM. Is this perhaps the reason?