Wat? It obviously isn't. Scandinavia is characterized by mutually intelligible languages (at least in theory), and Finnish is clearly unintelligible. It is part of the Nordic countries though.

That's funny. I immediately noticed in me "what?! It clearly isn't!". Not sure why I have a strong opinion on that, but I find it enlightening in this context.

As a Swede, I've honestly never heard this being debated.

As a not-Swede, I know it as a friendly joke by Scandinavia and the World [0]

[0] https://satwcomic.com/no-invitation