Swedish and German are very closely related languages, so you probably had tons of implicit intuition about how Germanic languages work that didn’t have to be studied.
They're definitely Finlanders. Rooting for Finland in Finland - Sweden sportsball games, general disdain for Swedes as "sissies", etc, etc.
Source: I'm an immigrant from Sweden to Finland; my son is a Finland-Swede.
Alternative source: I think I've read somewhere on the internet (or seen in some YouTube video?) an offhand quip along those same "Sissy Sweden-Swedes" lines by the internationally most well-known -- at least among the kind of people frequenting HN, I'd assume -- Finland-Swede, Linus Torvalds.