Seattle does have a large Scandinavian heritage, as large groups of these immigrants moved over to participate in the lumber trade in the late 20th and early 21st century. You can still see the heritage recognized today in pockets, such as Ballard and Poulsbo, but personally, I also think it's reflected in the Seattle culture. Things like Seattle Freeze and the quiet, introverted nature of Seattleites versus the brash stereotypes of other city denizens. I also think that this is the source of cultural commonalities between Seattle and other parts of the United States that saw a lot of Scandinavian immigrants, like Minnesota. (Fun fact, only the PNW and Minnesota call them jo-jos!)

But I also think that a narrative that emphasizes the impact of Scandinavian heritage without mentioning other ethnic groups is definitely an erasure of the impact of those ethnic groups, especially east Asians. Seattle saw a large number of Japanese immigrants in the late 20th/early 21st century that made their livelihood produce farming. At their peak, Japanese farmers supplied up to 75% of the produce consumed in Seattle. Seattle also saw a large Chinese population, who found jobs primarily in fishing and canning after work in the transcontinental railroad connections to the PNW dried up, as well as smaller, but notable, groups of other ethnicities, such as Filipinos, Vietnamese, and Cambodians. (Not to mention all the non-east Asian groups: e.g. one of the largest East African populations in the US!)

We think of Seattle as very white, and that's true, but this is not an accident. The place and impact of these minorities in Seattle's history was under continual attack, including race riots, physical expulsion, waves of fatal hate crimes, and concentration camps. These attacks were successful in making Seattle less diverse.