The purpose of misleading about “politician did X” is to sell a call to action. Any time there is a call to action supported by a claim, there is an obvious motivation for misrepresentation (the very same one present when “politicia did X” is the claim.) This contains a call to action, ergo, it has an obvious motivation for misrepresentation.
> I don't think it demonstrates much that students believed it.
I think it demonstrates a lot that half of 13-year-old students in the US study believed a page which referenced a fictitious nation-state in the Pacific Northwest was reliable, leaving aside the other indicia of deception. Though whether what it says is about internet literacy or complete failure of education on geography perhaps less clear.